Well, there's been comment made in another thread that RPG books are primarily bought to read and collect....so to ask the question, which are yor favourite games to actually play?  Mine, in order:

1) Mage: The Ascension - actually, one of the few games I played exclusively for years, while magpie-ing various other games' ideas to use within it.
2) Traveller (mainly the Mongoose version) - respect Classic and others, but play the Mongoose game. Just finished a year long campaign, and will duly be setting up another campaign in a few months when the next edition arrives.
3) Dungeons & Dragons (as part of Adventurer's League)
4) Call of Cthulhu - curiously, mainly oneshots these days.
5) RuneQuest (or Pendragon) - the brackets for Pendragon because, honestly, I don't play it although I want to. I have played a bit of RuneQuest though.
6) Feng Shui - One Shots again - very easy to play.
7) Unknown Armies - although actually, it's really that I tend to use the scenarios for other games like Mage. I've also used them for Doctor Who games.
Vampire: The Masquerade - I feel uncomfortable, but I've even LARPed this before.
9) WFRP - Not so much now, but frequently played in my past. Not so keen on the 40KRP titles however
10) Paranoia - yep, it's a one shots thing again.

What are yours?

Here are the games that I've played in or run at least 2 adventures/scenarios over the past 8 years or so:

• RuneQuest 6 (and, previously, MRQII) [2 campaigns + shorter adventures]
  
• Call of Cthulhu (6e/7e) [2 campaigns + shorter adventures]
  
• Dungeons and Dragons 5e [a couple of adventures]
  
• Advanced Dungeons and Dragons (TSR era) (sometimes with OSRIC help) [short campaign]
  
• Crypts and Things (and, previously, house-ruled S&W) [campaign + one shots]
  
• OpenQuest [aborted campaign]
  
• Basic/Expert Dungeons and Dragons (TSR era) [some adventures]
  

I thinks that's it.  I've played a number of other games, but only as 'one shots' (one adventure, though perhaps extended over 1-3 sessions).

I wish there was more...

Top ten seems a bit much for me.  Here's my top five:

1) Call of Cthulhu (d20 1st, 6e 2nd)
2) Shadowrun (1st ed. with some house rules)
3) D&D 5e
4) UGS (my own d12 gaming system that was never published)
5) Star Wars d20

My favorite games to play are:

TSR/OSR D&D. Especially of the B/X or BECMI/RC lineage. Nowadays I favor ACKS. Got half a dozen of adventures I'm itching to run, but a long-term game is what I really want.

D&D 5e. Great vehicle for AD&Desque as well as new school adventures.

WFRP. Like D&D, only with sides of historical caricature, black powder and gallows humor.

CoC. One of my fallback games for off-the-cuff one-shots.

Runequest/Stormbringer. For all fantasy campaigns when D&D won't quite cut it.

Mongoose Traveller. Ran it once, loved it, want to run it again.

oWoD and nWoD. It's not just for readers. Partial to nWoD mostly.

Savage Worlds. Another fallback game. Does two-fisted action like nobody's business. Gimmicky, but in a good way.

Rifts. Haven't run this in a while but with SW Rifts in the horizon... hoo boy.

I don't have ten that I like, never mind that we play:
1) GMC-nWoD - we use this for a lot of stuff; right now Werewolf: the Forsaken 2nd edition, but also a Mass Effect hack.
2) 13th Age - with a custom setting
3) ACKS - hacked for a historical game
4) M&M1e - hacked for a historical horror-supers game

That's it for my group.

Since I started gaming again in 2013, I've played:

D&D 3.5 one campaign as a player.
RuneQuest 6 two campaigns and several one shots. This is my go to game these days. Mostly running it for others, trying to spread the word.
Call of Cthulhu several one shots, as player and GM.
Trail of Cthulhu several one shots. This actually works really well for one shots. Not sure about how campaign play would shake out.

I'd love to play some D&D 5E but haven't had the chance yet. Would also liked to play some nWoD, but haven't found people to play with. I'm one of those people that has the books and mainly reads them, sorry! Just hasn't been much interest in my group or in the local MeetUp. No, I tell a lie, one guy is running an Old West Mage game, but it started when I was in the middle of my thesis/baby perfect storm gaming hiatus.
Would also love to give Sorcerer a try.

• RQ6 and others of its ilk.
• Unknown Armies
• ORE, especially ADW and Reign
• BoL, using Honor+Intrigue as a supplement
• Apocalypse World and others of its ilk
• Sorcerer
• Feng Shui
• Unisystem Classic
• ORC, the system behind Fates Worse Than Death
• Legends of the Wulin

Fate/FUDGE, DCC, TRoS, Fantasy Age and Traveller almost made the cut, but were just barely defeated, with TRoS only losing on account of the non-combat rules:).

I would have added Savage Worlds, too, but I'm not sure how I'd like it without the "shaken" rule. Haven't played it since it was removed, so no opinion there.

Admittedly, GURPS 4e would have been there, too, but I don't own the books since I went digital. And the PDF pricing isn't to my taste, so I haven't repurchased the corebooks;).

Pendragon and Maelstrom would be there, too, if I had enough experience with them. But as it is, I've only played or run them shortly.

Oh, and did I mention Exalted:D?

I don't really play many different tabletop RPG's, though if I thought about it, I end up using material from other books. The rules in play are almost always a mix of GURPS or sometimes TFT usually with house rules and some things adapted from non-GURPS/TFT books, so roughly:

1) GURPS 3e/4e houserule/foreign-rule hybrid.
2) GURPS 3e with house rules & some adapted foreign rules.
3) TFT with house rules & some adapted foreign rules.
4) TFT nostalgia mode without house rules.
5) The Desert Environment (adapted to house rules)
6) The Mountain Environment (adapted to house rules)
7) Aftermath (adapted to house rules)
Phoenix Command (adapted to house rules)
9) Palladium Weapons & Armor (adapted to house rules)
10) Ars Magica (adapted to house rules)

In Order
1) Call of Cthulhu
1) Honor+Intrigue
1) Star Wars WEG D6
4) Runequest
5) Pendragon
6) Star Trek (FASA)
7) OD&D
7) Beast, Men, & Gods (an obscure D&D style FRPG)
9) Traveller
10) Boot Hill (the old version)
10) Empire of the Petal Throne

Honorable Mentions (in lexicographic order)
DC Heroes (the one with the logarithmic scale AP points just because they are so math-y and useful)
James Bond 007
Space Quest (for the 3D random sector star generation system)
The Fantasy Trip (this one should probably be in the top ten, but I'm just not sure what to bump)
Top Secret

Games not my own:

Look! Up In The Sky! by Klaxon Bowley, my son. Infinitely flexible supers game. I have run maybe a dozen campaigns of this, ranging from pulp to ultimate power rating, over the last three or four years, and the game has consistently rocked! Still not released, or even in Beta playtest, unfortunately.

Two Fisted Tales from Precis Intermedia. Love this game for pulp! No knowing post-modern winks, this plays straight, and nails it.

Hard Nova II from Precis Intermedia. Wonderful light-medium SF game, very flexible, very extensible, and very easy to play.

Diaspora by VSCA. Another sweet SF game, this one a Fate system. Slightly storygamish, but easily drifted into trad style.

Coyote Trail from Precis Intermedia. My hands down favorite western game. Sweet, simple, but very rewarding. Hits all my boxes!

Hearts & Souls from Silverlion Studios. My first supers love. Not as flexible as LUITS, but more deeply engaged in the comic book style. Extremely enjoyable!

My own:

In Harm's Way: Pigboats. I have never run a less than stellar campaign with this game. A joy to run!

Blood Games II/OHMAS/Outremer. Perhaps my players' favorite. I have had some outrageously awesome campaigns with this series of games!

Volant. The setting generators pretty much guarantee a cool campaign. I have used it to run vanilla fantasy as well as the standard airborne settings, and the generators work just fine, thank you!

StarCluster. Currently 3E, working on 4E. I have run this game so many times in so many different settings that it is as natural to me as breathing.

In Harm's Way: Aces And Angels. This is another favorite of my players. They ask for it often, and enjoy the hell out of being pilots.

High Strung. There is something so fun about being a rock and roller! These campaigns have been funny as hell in a black humor sort of way, with the players having to balance stealing Hope from their bandmates in order to keep on keeping on, with the reality that if you steal too much, the bandmate will fold and leave.

I can't do a particular order, but the ten would be something like:

1) Call of Cthulhu
2) Monster of the Week
3) D&D
4) Amber Diceless
5) Microscope
6) A Thousand and One Nights
7) Savage Worlds
Truth & Justice
9) Buffy the Vampire Slayer RPG
10) Hero System

My favorite games to play and I have played:

1. DC Heroes (Mayfair)
2. Star Wars d6 (WEG)
3. Marvel Super Heroes (TSR)
4. D&D BECMI (TSR)
5. d20 Modern (WotC)

One thing I love about theRPGsite is that people here actually play RPGs.

Things played in the last two years

Microlite74
Call of Cthulhu
RuneQuest 2nd edition
Vampire 20th
BRP/d100 Scifi
Fate Accelerated
In A Wicked Age
Cthulhu Dark
D&D5


Things currently running

A Microlite74-Fantasy Trip-Cthulhu Dark-Rippers hybrid where all the rules and stats are behind the screen, so to speak.

-D&D5e (As part of the Adventure's League)
-Mutants and Masterminds 3e (Every Sunday!)
-Feng Shui 2 (PBEM)
-HERO System (PBEM)
-FFG Star Wars (on hiatus, cuz my crew are spazzing)
-OVA (Off and on, and mostly online, same crew as FFG SW.)
-FASERIP Marvel (This is randomly when another player wants to do something instead of my M&M game.)

Sadly, s'all I got at the moment.

I'm trying to focus on systems/gameplay rather than settings...
Call of Cthulhu (in various modes, not all of them Lovecraftian or even horror)
Magic World My current go-to for various flavors of fantasy. It pretty much covers Stormbringer and WFRP for me as well.
Dungeon Crawl Classics
Runequest 6 (I haven't gotten to play all that much of it yet but I quite liked it and I'm about to start up again)
Lamentations of the Flame Princess More for its adventures and setting assumptions than any particular mechanical notions.
WEG Star Wars (despite not being much of a Star Wars fan)
Classic Travellerwith or without the OTU.
GURPS (though it's been a while and I've grown less fond of ads/disads)