... You do know that having the best DPS potential does not equal being the best kit, at all... Don't you?
If you really meant having the best dps potential, then you need to make a distinction: best spike dps (possibly the most important) or best sustained dps (not that important)? If it's spike dps then it's QMS > possibly Tsol > destroyer > Hsol. If it's sustained dps it's probably destroyer > QMS > Tsol > Hsol... At least until you run out of ammo. Which sometimes is relevant...
On the other hand, if you meant best kit, which I think you did...
The destroyer has an awesome damage output potential, stagger immunity, OMGfucking good grenades as well as great accuracy and magazine boosts. It would be a clear candidate for n.1, until you notice... The speed reduction and no dodge. Given that mobility > else in this game, it goes from n. 1 directly to n. 4. In addition, it also lacks a way to insta-refill the magazine... One more reason for a definite n.4.
Hsol is awesome. Although it's slightly behind as far as dps goes, it actually uses many less bullets to reach that dps, which for example makes it a better harrier platform than the tsol/QMS. Some form of CC in CS, and a real grenade make it almost on par with the awesomeness that are the other two kits. In the end, the only thing that sets them apart is that the Hsol needs a good gun: he can't turn a peashooter in an awesome weapon like the MM kits can. So I reluctantly place him 3rd. Reluctantly because it's still an awesome kit, and very much underrated around here.
Tsol and QMS are so similar it's hard to pick one over the other. The turian is surely more user friendly, having some pretty good CC powers. On the other hand, the Quarian has a better debuff and, more importantly, a dodge. All in all, I'd say the turian wins on consoles due to the stability bonus being meaningful there. On PC, they're pretty damn equal. The turian is still more stylish though