One thing I can think of that Japan has going for it is the random collectible aspect with the toy machines all over. I think I've seen them referred to as Gashapon? As long as they're not too expensive, I could see that being a big hit.

This raises a few questions about form changes...

I guess Skylanders must be a pretty big thing over in Japan too for Bandai to make this happen.

Well, either that or Pokemon Rumble U's figures were a success. Or, hey, maybe it's Disney infinity that's making it so cool in Japan.
And now we have a problem that people had when Disney Infinity came out; it's ripping off Skylanders. Let's look at each game's unique aspects;
Skylanders; Swappable characters, being able to trap characters in toys (Trap Team), and cool cut scenes.
Infinity; Fun worlds, Disney characters, sand box (I guess), and Toy Box.
Rumble U; cheap figures, okay cut scenes, and Pokemon (but only a few).
So in each game this kind of thing is done in, they each, at least, include some different aspects. Now let's look at;
SummonRide; Elemental Groups (Skylanders), Characters people are mostly familiar with, disks (Infinity)...that's it. There are no more things that are unique about it so far!
If you want people to buy your game , you show them what makes this game different from other games. Who would by Pokemon X or Y if Nintendo just said "It's basically the exact same f**king game as the past 20 in the series! But with better graphics. No new gameplay, no interesting story to make it different from others, but better graphics!" Yeah, in this case, the Kamen Riders are the better graphics.
Maybe if the game included some bike figures you could use in-game. That hasn't been done with this category of games before! That would be cool! If you add Showa Riders, it won't make a difference, there'll be no new gameplay.
Every video game does something different. And I like that. Look for what's new and not what's been done before. But all there is for this is Kamen Riders. And that's enough to get people hyped to buy a game that unlocks heroes & levels with real-world currency.

probleam is the fact xbox 360 is region locked where as ps3 ant region lock so you can play imported games.