I don't think that's considered winning...

Eitherway, Kuuga blows up the world, so he wins...unless Fourze is chilling in his moonbase.

All of Kiva's forms have an Emperor form as well.

Anyway, I'm voting Kiva.
The presumption that Kiva's Emperor form is weaker than other Final forms is on the basis that he uses it for a lot more of his fights. Yet it's never taken into consideration that, possibly, the Fangire are stronger than the Grongi.
Kiva also held back in all of his fights, explaining the bat thing (Forgot what it was called) on the Zanvat saber.

Concerning Double, I'm not sure. FangJoker is removed from the equation in that Shotaro can't become that form, forcing him to de-transform, a huge liability. Double's versatility is his greatest asset, but I just don't see him winning it.

That, and if literally stopping time isn't enough reason for Kabuto to defeat Decade, blowing up a city street isn't enough reason for Kuuga to defeat these two. -3-

Kabuto doesn't stop time. He just moves at a speed that makes it seem like time has stopped.

And again, RAINBOWS OF DEATH. 'NUFF SAID.

Fair enough.
The point is: Kabuto is not moving at super speed. Time around him has slowed so that he's perceived at super speed.
That means, regardless how fast you can move (Decade, Faiz, Accel, etc), they would always be statuesque in how Kabuto would perceive them.
Hell, Kabuto has reversed time multiple times.

Anyway, before I derail any further, still going with Kiva.

This isn't even close, Kuuga.

Okay, let's set powers aside and look at how the characters' minds work for a second. So let's look at how these guys handle stress. Yusuke never gives up - if he's not up to a challenge he'll train himself until he is, even if involves getting himself shocked with a defibrillator to send his belt into extreme overdrive with only a vague idea of what will happen. Wataru, meanwhile, travels back in time to stop his own conception because he'd rather not exist than cope with shit. Kuuga definitely has the mental edge here.

Darn right you voted Kiva >D

I can do that. And anything I can do, a Rider can do, isn't impressive. Kiva breaks daylight! Can you break daylight?

Kuuga may handle stress really well, but Double doesn't get stressed. If he's defeated, he calmly googles the way to defeat his opponent. True, Shotaro was helpless aainst Terror's attack, but he got over it, and Phillip was immune anyways. Besides, the attack was meant to cause terror, and only a few people were immune.

And again, RAINBOWS. OF. DEATH. (If this doesn't become a meme, I'm moving to Neptune).

So what happens if it's a tie?