Mega Turrican is quite good, though I have already played it. I'll abstain from voting, since I'm not in the mood for the other two. I will absolutely use this as an excuse to replay Mega Turrican if it wins though.
Hmmm, looks like I'm out on this one. Don't own the first two, and while I do have Code Veronica, I've never beaten any Resident Evil (yeah, yeah, I know) so if I was inclined to do so I'd start with the first.