primecoin, riecoin and gapcoin all innovated different useful PoW algorithms. Regarding the technical innovative aspects, Riecoin is the best (of course, I'm Riecoin's dev).

sapience uses a lot of buzzwords but nothing technical, they didn't innovate anything yet. It's vaporware, they have a 14min video that actually says nothing, and if you ask me... it smells bad

ethereum includes a turing-complete script language that allows for lots of kinds of smart contracts. I think it's still vaporware (ie they didn't deliver yet), but there are techincal discussions were they show competence and what they claim is possible and might actually work