I know you said you didn't do RPGs, but it's hard for me to go into recommendations without mentioning them. They're fun.
360: Bayonetta (360 version runs smoother), Gears of War I & II, Mass Effect (note:RPG), Tales of Vesperia (also an RPG), Earth Defense Force 2017 (not an RPG), Deathsmiles.
PS3: Demon's Souls, Valkyria Chronicles, Uncharted I & II, Disgaea 3 & 4 (note:SRPG), LittleBigPlanet, Malicious, Wipeout HD/Fury, Wizardry: Labyrinth of Lost Souls (note: dungeon crawler RPG).
Personally, I've been enjoying the PS3 more lately. A lot of the stuff on the 360 is also on the PC, after all. Then again, I am the kind of person who compulsively fills in every map he's given. I also have no idea which console is superior when it comes to online multiplayer. I don't play it, so I don't know what the PSN crowd is like nor how the servers behave. If that aspect is important to you, take my opinion with a grain of salt.
Most of the big games are multi-platform, though, so it shouldn't be too much of a big deal which one you pick. The PS3's library is by nature a little bigger than the 360's since you can import games from anywhere without worrying about regional lockout.
[sub]Because seriously, fuck regional lockout.[/sub]