#2 is the strongest cover for my money, it's clearly Ghostbusters but there's clearly more going on thanks to the Edgar Allen Poe, the crucifix/bible, more serious armour, and the modern ghostmobile and so on (I always like it when an RPG setting with obvious inspiration has more going on than the inspiration, esp. if it's easy to pare back as needed). So that's immediately "tell me more" and would be what would interest me and I think my group.
#1 is also strong, particularly as it has an armoured humanoid dinosaur with a gun. #3 just makes me laugh because of the goddamn Cutty Sark, but I imagine most readers won't know what that is, and Montana Drones is a bit too on the nose - though that it's about Indiana Jones is appealing. #4 conveys what its about well, no confuse, but is uninspiring in an era when similar art is quite common (c.f. Tales from the Loop etc.). #5 really destroyed by that logo in the bottom left, like I couldn't "get" what I was supposed to be seeing conceptually for a while there - take away the logo, and I think the vibe is TOS-era Star Trek, Forbidden Planet, and so on. With the logo, it just looks weird.