I saw a couple of episodes of Gundam Wing and G Gundam when I was a kid but not enough to get me hooked on either series. The first series I watched with any kind of dedication was Gundam SEED, which I think did an excellent job of serving as a series introduction (it also probably has something to do with why I'm much more forgiving of Destiny's numerous flaws than most people I talk to). My first super robot series was Evangelion, which I only watched to see what the fuss was all about and never finished, and then GURREN FUCKING LAGANN several years later.
More recently I'm working on getting some more "old school" experience under my belt; so far I've chewed my way through a good chunk of G Gundam and all of GaoGaiGar and GGG FINAL. Currently working on Gravion.