Just curious what people like in terms of systems that support all of the PC's being some sort of magician in some non-D&D fantasy settings. I haven't found one that's a really good fit for me yet.

Unknown Armies 3e: it's actually a very good system. However, the magic is (a) focused on the shared-reality-consensus thing (not a huge fan of that) and (b) most of the magic schools and stuff are weird (which I like), but weird in a way that I'm not into. Also I can never wrap my head around why you couldn't do folk magic or hermetic magic or something like that, since there are lots of people who believe in it. Also the only antagonists are other magicians or things created by them.

Chronicles of Darkness 2e Mage: also very cool, but the magic system is pretty complicated, and its so powerful even at low levels that it can quickly become impossible for an average GM like myself to figure out how to run a game given that players can do so much so quickly. Does not rely on consensus reality, so that's a plus.

Also completely free-form magic always seems not very magical to me, it seems more like psychic powers. Having to find old tomes, do difficult rituals, comply with some set of principles seems more magic-y to me. Free-form systems always seem more like psychic powers (X-Men or something).

Stuff like Dresden Files Accelerated isn't really built for "everyone is a magician" - at best it's "one guy who is a magician and whose powers are so broad they're much more effective than anyone else overall.

There's also Nephalim (old don't know much about that); GURPS Thaumaturgy / Cabal/ etc. - great Ken Hite stuff but I'm not that into GURPS; BRP (lots supplements for a bunch of different systems but I'm not sure there's a good "everyone is a sorcerer"; Ars Magica (I think again that's freeform, plus you spend most of your time playing some guy that works for the OP wizard); lots of "modern" OSR supernatural games, but again they're not "everyone is a wizard" and also they're usually just reskinned vancian D&D magic; Esoterica which is cool but the magic part is mostly a list of generic superpowers (like you find in Savage Worlds). Old World of Darkness had Hedge Magician (Sorcerer), which is kind of neat and did feel real-magical.

Is very doable with gurps, you could have everybody some flavor of wizard using very different systems that are all designed to work together.

I'm quite fond of their ritual magic system, and if you can find their Voodoo third edition book(I think it's voodoo) it has a creepy cool setting to it.

Also there's C.J. Carella's witchcraft, but that's mostly only 2 types of magicians, and the "spells" are more like powers (you have a fireball skill).

"Enlightened Magic" for BRP is a good supplement you might want to check out for this kind of thing. It goes into sufficient detail for an all-spellcasters game and is highly suited to modern settings. Mythras also has five distinct magic systems designed to be customized to fit the setting.

I was thinking BRP but use some of the cool GURPs settings. I wonder if I could use a simple core engine like open quest or revolution d100?

Ars Magica is the really, really, really obvious one.  Doesn't fit everyone's play style, but it's exactly what you're asking and I think it's extremely cool.

Here's my homebrew rebuild of the Mage the Ascension ruleset (which came to be called "White Book Mage" in my area because I gave out printed copies of it to all my players in white binders); feel free to use it in whole or in part.

White Book Mage the Ascension

Neat

I found the very cool Dark Ages Mage and it has a great system that feels alot more like "real" magic (where paradigms are much more important).

I looked at my old Witchcraft Unisystem stuff and forgot just how clever C. J. Carella was.

For those of you that are Unisystem people, when you run Unisystem do you use Cinematic and port stuff over from Classic? Still use classic w/ some house rules? the big difference with cinematic if I remember is you have hero points and a simplified skill system.