Lets be honest, XBox Live Arcade has some crap on it, it also has some good games, Braid is probably the first great game.
Its a simple proper old school puzzle platformer that would feel at home on the Amiga. Controls are simple, move left and right, jump and rewind time. There are bad things that you can kill by jumping on their heads and big doors that need big keys to open them. Rewind time has two uses firstly when you die you just rewind to before you died and try again, secondly it can be used to reset things like you can see in the boss fight below. Time is a major factor in the game too, some levels the bad things will move forward in time as you walk right, stop when you stop, and move back in time when you move left. This adds to the puzzle part of the game even more as on hunt levels you have to kill all the bad things to collect the jigsaw piece (forgot to mention, you collect jigsaw pieces) and you need to kill them in a certain order that can take ages to work out as when you move left and back in time any bad things you kill come back to life.
Its 1200 Live points, which seems expensive compared to other arcade games but thats because its head and shoulders above everything else and its not the sort of game you are going to get bored of after a couple of hours
Braid