I downloaded two very interesting games the other day via XBOX Live Arcade, and even though they were just the trials (you download the entire game, but can only play a small portion before having to buy it to unlock the full experience), I came away thirsty for more!
Lara Croft and the Guardian Of Light
This sort of spin-off from the famed Tomb Raider franchise is displayed in a unique isometric almost top-down view-point, but all the old Tomb Raider exploration and puzzling is intact. Graphically the new look is very fresh and detailed and harks back to PC games like Diablo. The trial lasts a while too and we get to experience some of the major gameplay, boss fights and different environmental exploration moves and gadgets.
Getting lots of buzz this one, basically a 2D platformer set in a strange black & white netherworld that is supposed to be some kids dream as you control a small boy and traverse the environments with just the ability to jump and push / pull things. The world is full of dangers such as bear traps and giant spiders (!), but the look and feel is captivating, creepy and full of atmosphere that like Lara, this is a game I will certainly be purchasing at a later date.