The SF comics are on hiatus until the Summer while Udon works on the HD SF game. There’s four TPBs that collect everything if you want to check those out. I’m fairly sure Udon doesn’t do subscriptions (or at least they never mentioned it here during their modding tenure IIRC) only Pre-Orders via comic book shops. So you’d have to wait about 3 months prior for it to show up in Previews, Spring 2008 at best.
Udon’s been translating several SF manga from Japan so you may want to check those books out. All of them have had influence on the video games from creating Karin, Evil/SNH Ryu, designing Gouken and so on. There’s SF2 (one book is out), SF Zero (both books are out), Sakura Ganbaru! (both books are out) and SF3 Ryu Final (one book is out).
X-Men is still going strong and after Messiah Complex they are doing their regular ‘big ass crossover just ended so this is a good jumping into point’ ordeal. Both Uncanny by Brubaker and X-Men by Carey are really good.
On the DC end, All Star Superman and Detective Comics (ONLY when Paul Dini writes it) are both really good and very new reader friendly.
Some other gems out there I haven’t mentioned. If possible, I suggest either going to a comic book shop and seeing what is that you like, or even book stores that carries TPBs that lets you sit there and read material for free before you make any decisions. Just so you know what the artists / writers are like prior to comitting to anything.