by Elstree
Yet another endorsement of Claustrophobia. I've yet to meet a Heroscape fan who did not also love this game.I'll also echo the endorsement of Mice and Mystics. It's a great dungeon crawl but with a much stronger emphasis on the story than you find in other games. It's also a great family game if you have children.
As for Touch of Evil, it's a good substitute for Arkham Horror when you don't have four hours to spare. However it sounds like you're already a big fan of Arkham Horror so I don't know if this one is really going to fill a gap in your collection.
I like the mechanics of Last Night on Earth much more. If your group doesn't like zombies, you might consider Invasion from Outer Space. It uses the LNOE core game rules but is themed as performers from a travelling carnival versus invading martians, with a 1950's b-grade sci-fi feel.