Apart from Godzilla and Chuck.
Kabuto doesnt really reach my path of heaven. Tsukasa was average at best as Decade, even when killing Riders, most of them off-screen. Decade's powers are unlimited, like the Dummy dopant, only problem- the user is a blob. Hell, I'd be 10xtimes better as Decade, hence my name.
Den-O can get a Super-Ultra-Amazing-Overpovered-ChoClimax form and still be at par with Ryuki (IMO Ryuki is the weakest Rider, flame away at will)
My vote goes for Agito. He's like the Zeo crystal, getting stronger and evolving constantly. Meaning he could Rider kick everything with his deep Agito-ish breathing. His whole theme is about evolution. (lol)
I'm really behind on Ultraman series som my opinion is bound to be flawled.
For sentai- Gokaigers. Yes, they are multiple Decades, meaning unlimited combos and powers in combinations beyond awesome. If the next sentai isnt about childrens of different Gods, then pirates will always win.