Dynotaku

I'd suggest picking up the Shooter Pack that's on STEAM right now for $20. It has Alien Shooter and Zombie Shooter, they're almost the exact same game, but they're worth the money - and they're both the isometric robotron controls. Visually they're a throwback to Diablo 2, mostly sprite, but mostly sprite, and the nice thing about that is the persistence of gore, and some of the levels have over 1000 monsters in it, and they die quite nicely. Most of the levels are wall to wall red by the time you're done.