What game
systems have I
tried that made me go WOW?! Hm, let's see.
Pendragon. So different from what I'd played until then, and it was an amazing (if far too short
) campaign. In fact, playing it impressed me so much, that I bought a copy some time later, and ended up nicking some of bits of the system and porting them to D&D.
Call of Cthulhu. And how many games has
this one influenced, I wonder. . . A timeless classic, and yeah, there are reasons for this. Try it, with a decent GM, and you'll find out why for yourself. . .
Dragon Warriors. A fantasy RPG with *soul*. Has an excellent, evocative setting built in, great names for just about everything, from places to NPCs to spells, and so on. Plus, a neat, fast, intuitive system.
Ooh, colours! Anyway, those games all blew me away when I had the good fortune to try them.