klaymen: Chaser has a slower gameplay and some passages are downright boring (sniper mission, underwater, some parts on Mars) so you probably won't like it.
While Iron Storm's story is quite original, I did not like the scripting and omnipresent snipers. Heck, I did not even finish the game.
Painkiller is Serious Sam-ish shooter. Enter the room, kill horde of enemies, continue. While it's a brainless shooter, I quite like it.
Pain Killer is nice in that it dispenses with any pretense of being about anything other than shooting things up.
Personally, I liked Unreal more than Quake, and DN3D has an amazing source port and in the near future new indie recreation.
Serious Sam is hit or miss, if you appreciate the parody and the humor it's great, otherwise it's a complete waste of time.