I'm not a GM, but as an extreme survival horror fan, I am going to give my response anyway (and I apologize that I am in fact replying to a thread in which the original topic creator said he only wanted GMs to reply, and I myself am not a GM..).
So yeah, survival horror. As the poster above said, DOOM III isn't survival horror. It's survival yeah, semi-horror.. more of a thriller than an actual psych. horror game (like Silent Hill).
So next, let me answer your question which I can actually answer. Will RE and SH remain the powerhouse series' in the next generation of survival horror? I'll be brutally honest. I don't think so. Well, kinda.
RE's been around forever. I don't think they're going to leave anytime soon, and I don't think the series is going to stop delivering to their audience what they deliver; cheap scares and lots of gore. They've perfected it, I must say, and even though this isn't my thing, I can honestly say RE does a damn good job at delivering the gore and stuff.
Of course, if anyone here knows me, they know I'm a huge Silent Hill fan, and despise everything Resident Evil offers. HUGE. But, as much as I LOVE the series, I have to admit the most recent game in the series (Silent Hill 4: The Room), while it had its good points (the prison), it was a bad game. As with so many game series' out there, the first was by far the best. The second was almost as good (stunningly beautiful storyline), but went downhill with #3 (far too much reliance on action and gore -- just like Resident Evil) and hit a low with #4. Now, there is a Silent Hill 5 supposedly on the horizon somewhere, but I know nothing of it. Team Silent can in theory bring themselves back by going back to their roots (a psychological horror story which relies more on atmosphere and story than on gore and killing), but with the last two games going further downhill, I dunno.. I'm losing faith in Konami and Team Silent.
Yes that's right, I.. chris, mc, masterchris, biggest Silent Hill fan on Game Revolution, whatever you want to call me, am losing faith in the Silent Hill series. It's got a solid foundation to build on, and the possibility is there for the series to be great again, but I just don't think the developers want to go there; they want to follow behind Resident Evil, for whatever reason.
So to sum up my ramblings, Silent Hill is the greatest horror series ever, but the future is murky. If you're into action and gore, I think Resident Evil and Silent Hill's futures are for you; but if you're more into what I'm into (movies like Ju-On, Jacob's Ladder and the Blair Witch Project), I think the future of Silent Hill isn't that promising. We need a new series to bring us the psychological horror we crave, and at the moment the closest things we can do are replays of Silent Hill and SH2, or the ever fantastic Fatal Frame series (highly underrated, almost as wonderful as Silent Hill, and spooky as hell).
Did that make sense?