If you've never played any before get Storm 2. You dont have online, so that mode is useless to you, and Storm 2 has the absolute best campaign mode of any of these games in my opinion. The boss battles are also insanely good. I cant vouch for Storm 1 since I have a 360, but I do know Storm 1 is just battles with text inbetween to fade the scenes. Storm 2 features a full RPG type gameplay between fights/boss battles and is a ton of fun.
Also incase you didnt already know, Storm 1 covers the entire Part 1 of the series (but skips some things, like the sound 4). And Storm 2 covers the beginning of Part 2 all through the Pain invasion.