Gundam is pretty decent, but I always felt was a little lacking in depth. It's like every series has to be 50 episodes long so they unnecessarily stretch them out. But I've only seen two of the series, so I may have no idea what I'm talking about. Other mecha series that are interesting and worth checking in to are: Giant Robo, Evangelion, RahXephon, Escaflowne, and Gunbuster.