It'll be hard for someone to top Guerrilla Bob. It's got two types of survival( normal and wave attack), and two types of story modes. The graphics are ace, polished and detailed. Plus, John Gore is not only the final boss of story mode but, also becomes a playable character. It's got almost any weapon you can want and most are upgradeable.
I'd say minigore over that because of the graphic style.. I don't like the slight cartoonish look of Guerrilla Bob but I like the simplistic look of minigore... Sure GB has more crap put into it but half my vote depends on presentation. So minigore (then pirates tresure)
A4E:R, it's actually really challenging at times, especially if you try to finish all the challenges.