I aim to please. I'll post more ideas when I can think up some.
This is hard, since OOO and Kabuto are out, so I can't use OOO's forms as an anchor for themes :p

Who has the best coverage?! (Den-O Climax Form vs Faiz Blaster Form)
Here Kitty Kitty! (Beast vs Tiger)
Obvious Match is Obvious(Joker vs Wing Knight)

I'll think of a few later,its tough.lol.

I thought of one this morning for a Decade v Fourze match up.

Fourze Cosmic States

vs

Decade Complete

They both encompass the full power of their collected power, and would make for an interesting match. Long as people vote right and not against Decade solely because they hate Decade.

There's a rule which I live by -- if it's funny it overrules anything! :lol

And they're both two of the most clusterfucky ultimate form suits!

Anyway, I just had an idea, too. Kaixa vs. Kengo Ixa vs. Armed Kiriya vs. V1 from Agito - battle of the Toshiki Inoue asshole supporting characters!

Wizard vs Fourze.

Not just because of the obvious "Friendship is Magic" connotations, but I want to a fight between a spam attacker and a spam defender :lol

Voted Showa. Won't win, but whatever. I'd personally love to see some Showa vs Heisei matches, as well some Showa vs Showa and Heisei vs Heisei.

MATCH UPS:

Old vs New: Ichigo, Nigo and V3 (Showa) vs Ichigo, Nigo and V3 (Kamen Rider The First/The Next)
Space Heroes: Super-1 vs Fourze
Here There Be Dragons: Ryuki Survive vs Wizard All Dragon Form
Neo Heisei Secondary Rider Throwdown: Meteor vs Beast vs Birth vs Proto-Birth vs Accel
The Time Traveler vs The World Destroyer: Den-O vs Decade
Who is Strongest (Showa Edition): Ichigo vs Nigo vs V3 vs Rider Man vs X vs Amazon vs Stronger vs Sky Rider vs Super-1 vs ZX vs Black vs Black RX
Organic Rider Showdown: Shin vs Amazon vs Another Agito
Female Rider Smackdown: Femme vs Nadeshiko
Card Games on Motorcycles: Blade vs Decade vs Ryuki
I'm Batman: Kiva vs Knight

Voting Showa. Because I'm up to the Showa point of Decade an the bits I've seen make them look at least as interesting as Heisei. (Cue everyone going "They Were Different And Sucky In Decade!). Meanwhile, my ideas for matchups:

Stop! Police!: G3-X Vs G-Den-O
It's a Jungle: Rey Vs Tiger
Those Jokers: Chalice Vs Glaive
Or...
Joker Vs Chalice
Feel My Sting: Birth Vs Sasword
Who needs a TARDIS?: Den-O Vs Odin
Dead All Along: Eternal Vs Ryuga
Fish are Friends, Not Food: Poseidon Vs Abyss

Also, are we still including Wizard and Beast in this? We don't know everything about their final forms, so...

Agito vs. Kiva
Den-O vs. Wizard

:lol these sound like Xbox game acheivements (not that that's a bad thing)

Are we just going to forget Tackle? Or Larc? Or that one time Satonaka was Birth? Or that other time Kaixa was a woman?