My thoughts on a few, despite Rob's objection
...
Air Buster- Not a bad game, and certainly not long. There are sections where there are good sized masses of enemies that come on screen, making it a challenge to get as many of them as you can. The hard part with this, is that the arcade, Genesis and TG-16 ports are a bit different. The amount of enemies in the TG-16 version seems to be less than the Genesis or arcade (especially in stage 2), but I'm not certain just how different the Genesis and arcade versions are. It would come down to "who can blast the most enemies" in the end, though I believe it is possible to milk a boss or two, along with some spots in later stages (assuming the missiles that are shot out by stage 2's boss, and various missile pods, are worth score). I'm for keeping this one if we stick with only a particular version.
Hellfire- As much as I enjoy this game, the scores would all be pretty similar at the end I believe. Every stage has a set amount of enemies, and you're certainly not overwhelmed by their numbers. The end result would probably be scores that were insanely close, and/or tied. It's also a bit drawn out with it's slow pace, which would probably turn a number of players away. While I like it, I'd vote for removing it.
In the Hunt- It is a very slow paced game, but only in the sense of how fast it scrolls. It can get intense despite this, as lots of enemies from the water and the air make for quite a bit of dodging to offset at least some of the slower movement. I'd vote to keep it in.
Assault Suits Valken- Cool SNES game? Yep. A shmup? Not as far as I know. It's more of a cross between "Run 'N Gun" and "Action Platformer", than it is a shmup.
Captain Skyhawk- A fun NES game, but it really is a cakewalk up until the final boss. By the time you get to stage 3 roughly, you're fully powered, and the only way to screw up is not by getting caught up in enemy fire, but by slamming into something. The enemy count isn't particularly high either, so scores would probably be ridiculously similar. I'd vote for removing this one.
I'm still wondering how
1941 is "common", though.