Yajks! Minigore was not mention yet (or am I wrong?) you should check out Pirate's Treasure it has some more variability than for example Minigore Alive 4 Ever is cool too! for me: Minigore - every one knows why but still one level... gets old (sometimes) Pirate's Treasure - lots of levels lots of enemies - you should be entertained for a while A4E - Has quite the same idea as Pirate's Treasure but different setting
Gonna have to say Revolt... I love the destruct-able stuff and the explosions, really polished. Like Guerrilla Bob too.
Bug Heroes! oh wait, that's not out yet! Otherwise there aren't really any DSS on iOS that I really like...
Yeah, Guerilla Bob is an instant classic in my book. Pirate's Treasure was good, too, but it got rather repetitive after a long while.
Alive 4 Ever series, mostly Alive 4 Ever Returns. I cant wait for Alive 4 Ever 2 or 3 whatever its called.
There seems to be a lot of good options here so everything is pretty much covered. On that note, I think Guerrilla Bob is unloved and underappreciated.
I really think there are so many great DSS games on the app store that there is no "best" but more as personal favorites since there are a lot of great DSS currently available and soon to be available. We can all thank Robotron 2084 for starting it all 28 years ago.