Well, let's see. Sylar has telekinesis and various other things going for him. Spartans have muscles, strength, the phallanx, spears and shields. And the never give up mentality.

Ah, crap, but now Sylar has the ability to melt metal. There go the shields.

So maybe he could kill one, but then the 299 others would tear him into tiny pieces, I'm thinking.