I have to do all the work around here. Now I did manage to find some tidbits netyonder, but you guys might be surprised how many flagship games for the 360 aren't exactly HD quality. I picked a few examples out which I was pretty sure weren't old games 2008 or earlier, because back then, not too many games were decent resolution.
360
Alan Wake = 960x544 (4xAA) - As per gamefest presentation
Call of Duty: Black Ops = 1040x608 (2xAA)
Darksiders = 1152x648 (no AA)
Final Fantasy XIII = 1024x576 (2xAA)
Halo 3 = 1152x640 (no AA)
Marvel: Ultimate Alliance = 1280x720 (2xAA)
MK vs DC = 1040x624 (2xAA)
Ninja Gaiden 2 = 1120x584 (2xAA)
Prototype = 1120x640 (2xAA)
Sacred 2: Fallen Angel = 1920x1080 for any HD output (including PC res), 1280x960 for 4:3 output, 1376x768 for 480p widescreen (no AA)
Sonic Unleashed = 880x720 (2xAA)
Tomb Raider: Underworld = 1024x576 (2xAA) - depth buffer is 1040x576
Virtua Fighter 5 (demo) = 1024x1024 (4xAA)
PS3
Call of Duty 4 = 1024x600 (2x AA)
Jericho (demo) = 996x560 (2x AA)
Marvel: Ultimate Alliance (screenshot) = 1920x1080 (no AA)
Metal Gear Online = 1024x768 (2xAA, temporal)
Metal Gear Solid 4: Guns of the Patriot = 1024x768 (2xAA, temporal)
MK vs DC = 1024x576 (QAA)
Sacred 2: Fallen Angel = 1280x720 when sub-HD output selected, 1920x1080 for any HD output (no AA)
Silent Hill: Homecoming = 1024x576 (no AA)
Sonic Unleashed = 880x720 (blur filter)
Virtua Fighter 5 (screenshot) = 1024x1024 (no AA) , 1024x768 en mode 1080p
I'm not sure why fighting games prefer lower resolutions. Maybe so more alternate frames can be loaded at once, for punch actions or something. I highlighted Sacred 2 for the heck of it, because I'd expect a non-intensive RPG to have a higher definition. Maybe that's why FFXII is so low, or because it had to be multiplat, but I doubt we'll ever know on that.
And then there's this:
GT5 Prologue (demo) = 1080p mode is 1280x1080 (2xAA) in-game while the
garage/pit/showrooms are 1920x1080 with no AA.
So, Dev, if showroom resolution is what really matters to you, maybe I have a bone to toss you.
But what really surprised me was this:
XBLA
1942: Joint Strike = 1280x720 (4xAA)
After Burner Climax = 1280x720 (4xAA)
Battlefield 1943 = 1280x720 (no AA)
Bionic Commando: Rearmed = 1280x720 (no AA)
Boogie Bunnies = 1920x1080 (4xAA)
Call of Duty: Classic = 1280x720 (4xAA)
Commando 3 = 1280x720 (4xAA)
Dead Rising 2: Case Zero = 1280x720 (2xAA)
Hydrophobia = 960x672 (2xAA)
Ikaruga = 540x720 (4xAA, centered on 1280x720 frame)
Invincible Tiger = 1280x720 (4xAA, classic mode), 640x720 or 1280x360 (S3D mode), see here for more.
Lara Croft and The Guardian of Light = 1024x576 (2xAA)
Rez HD = 1280x720 (4xAA)
Serious Sam HD = 1120x630 (blur filter)
Splosion Man = 1280x720 (2xAA)
TMNT: TiT Re-shelled = 1280x720 (no AA)
Trials HD = 1280x680 (no AA, black borders)
Wolf of the Battlefield: Commando 3 = 1280x720 (4xAA)
PSN GAMES
1942: Joint Strike = 1280x720 (4xAA) or 1920x1080 (2xAA)
Blast Factor = 1920x1080 (no AA)
Bionic Commando: Rearmed = 1280x720 (no AA)
Calling All Cars (screenshot) = 1920x1080 (4x AA)
Commando 3 = 1280x720 (4xAA) or 1920x1080 (2xAA)
Echochrome = 1920x1080 (2xAA)
Elefunk = 1920x1080 (4xAA)
Forbidden Siren = 1024x512 (4xAA)
Go Puzzle = 1920x1080
GTHD = 1440x1080 (no AA) - Vehicle selection is rendered at 1920x1080
High Velocity Bowling = 1920x1080 (no AA)
Locoroco Cocoreccho = 1920x1080 (2x AA)
Mainichi Issyo = 1440x1080 (4xAA)
Pixel Junk Monsters/Racers/Eden = 1920x1080
Rocketmen = 1920x1080 (2xAA)
Rub'a'dub = 1600x1080 (no AA)
Snakeball = 1280x1080 (no AA)
Stardust HD = 1280x1080 (no AA)
Sudoku = 1920x1080
Super Rub-a-Dub = 1600x1080
Tekken 5 Dark Ressurection (screenshot) = 1920x1080 (no AA), not always?
Warhawk = 1280x720 (4xAA)
Wipeout HD = dynamic-framerate-dependent 1080p framebuffer (1280x1080 to 1920x1080)
Wolf of the Battlefield: Commando 3 = 1920x1080 (2xAA)