They're both good games, but the gameplay is VERY similar. I lost interest in the 2nd and still need to finish it.
I don't think you lose anything by doing #1 and skipping #2 if you don't feel like playing nearly the same game again. There are some better mechanics in #2, but not a huge deal.
Also, if you complete #1, you should get the option to import your character's powers into #2.