I like the original Mobile Suit Gundam anime. It's really old and the visuals aren't that good because of it but it's still worth a look and also featuring a story and not just random episodes like for the standard children series. The short series Gundam 0083: Stardust Memory also is pretty good...

I don't like most of the recent offsprings of the Gundam series as things often get really "kiddified"...