One thing I DON'T like about True20 is the boring base classes.
Yeah, that's something that's nagged at the back of my mind about True20, also. d20 Modern has the same weakness, even though I understand why it has what it has - but at least many of the advanced classes and prestige classes are more flavorful.
What I want in a RPG:
1. As hinted at above, give me lots of evocative archetypes to play with. Yeah, I know, some people call for more generic classes so they can build their own archetypes, but I like seeing actual classes or professions in a game with cool titles like Sector Ranger or Barbarian or Wizard that actually attempt to match game mechanics up with the image evoked by the class name.
2. Options - I like 'em. Give me lots of 'em. Unearthed Arcana, both the original and the successor, are perfect examples of entire books devoted to just plain options. The Psionics Toolkit is another of my favorite examples - a variety of cool goodies that made me actually become interested in psionics. But it's very important that options be included in the core - the 3.5 DMG is a good example. I want options so I can tailor my campaign to my taste.
3. Foresee the unforeseeable - that is, provide game mechanics to cover contingencies not addressed by specific game rules. 3e does this, but there are a lot of other games that have it also. Castles & Crusades, for example, has its SIEGE engine to plug the holes that 1e AD&D had.