These are all games that I would consider perfect 10s.
Geometry Wars - As sad as it sounds, if I had to have only one game for the 360, this would be it. I've played arcade shooters for decades, and I have my favorites like Dodonpachi, Mars Matrix, and R-Type Delta. This game is one of those types of games where after playing it for a while, and you start understanding enemy patterns, and how to avoid while shooting, it starts to become almost trance-inducing. The graphics are the kind where folks enjoy watching me play, as much as playing themselves. Learning that sometimes the best thing to do is NOT SHOOT, and swerve towards those blackhole things and allow them to take care of enemies for you, it becomes very, very addictive. There's only one other shooter that put me into that "zen" state while playing. But I couldn't say whether it would still do that for me, because I don't own a Jaguar anymore.
Soul Calibur - I remember loving SC in the arcades. It was a step up from Soul Edge, and after getting used to H+V+K no longer starting your supermove, and actually using the 8-way movement, it quickly became one of my favorite fighters. Then the Dreamcast version was released. Missions. New modes. New Weapons. New Fighters. Graphics BETTER than the Arcade. What's sick is that it could actually look better than what I remembered back in 2000. I played it recently on a 720p projector on an 82" screen, using a VGA adapter. It was
sublime.
Baldurs Gate II - It is an absolutely incredible RPG with damn near limitless replay value. I've only bought 6 PC games ever, and only two of them brand new. This is one of them. (CAVEAT: I've never played Planescape: Torment. I will change this soon.)
Super Mario All-Stars - Yes, its cheating because its a compilation. But WHAT a compilation. It took games that put Nintendo on the map, graphically enhanced them, AND included a (stupidly hard) game that wasn't originally released in the US. Its one of the 2 games that I'll never sell for my Super Nintendo.
Super Metroid- This is the other.
Halo Its one of those games that I didn't expect to like that much. I played through most of the game, and enjoying the story more and more as I progressed. Then a friend invited me over, and we played co-op on Legendary. It changed the experience. Now I was fighting for my life, and hoping that my friend could help me just get to Warthog so I could man the turrent gun. A year later, I would get to play 8-player using 4 xboxes. I've never had so much fun with a 1st-person shooter.