Contra: SS is an excellent run 'n gunner; it finally did justice to the Contra name with polygons. Not to mention the heavy rock soundtrack always gets me pumped up.
I had my doubts about Neo Contra for an incredibly long time, I hated on the game so much (without even playing it). After getting it back in October, though, I'll have to say it rocks...the soundtrack this time around is more of a techno music (and still rocks my pants off) and I definitely see traces of Metal Slug influence with the humor (ex: Bill & Jubei running on helicopter blades, the Animal Contra boss, the Russians doing that dance on top of the boulders, etc.). Neo Contra's a great game; maybe not as much as SS, but I certainly wouldn't mind another Contra in the same vein of it.
Thing is, where is the Contra storyline to go after Neo...and who knows if we'll ever see Bill Rizer again...I mean, the year was 4444 AD, after all.