honestly it's an action game and the story is bunk, you don't need the text or the voice acting. I have the japanese version but I speak the language and can say it's only a slight subversion of the typical "legacy of heroism has been handed down for generations and you must fulfill your destiny" trope.
I love Keio 2. The graphics and animations are beautiful, the levels are fun and well designed, and the shooter stages add some much needed variety. The only thing I didn't like is that it can be frustrating in places. Other than that, it's a great game.
I didn't feel like anything was frustrating, barring one level where the floors collapse and then later you need to spin a hamster wheel. Other than that, I enjoyed my time with it a lot. The last boss was a tad underwhelming, but still kinda neat.
Obviously the game isn't worth the price it goes for, but like with Saga, I still don't regret getting it since I had a lot of fun and will certainly replay it.
If you liked Keio 2 and you want more, there was an obscure demo CD for it in Japan, bundled with an art book, that has an exclusive shooting level. It is half of a placeholder so the graphics lean more on being absurd doodles than beautiful sprite work. It's expensive, but oddly enough not as expensive as the PAL copy of the game.
edit: it also comes with lots of bonus artwork on the disc (if the artbook isn't enough), better quality versions of the Mega CD FMVs, and info panels for the other fighters in the tournament. It's a very nice little bonus CD.
Personally between the 2 cartoony platformers we got in the west
We got a heck of a lot more than two cartoony platformers in the west. Pandemonium!, Clockwork Knight, Clockwork Knight 2, Bug!, Bug Too!, Gex...
Those either had obnoxious edgy characters, or were lifeless CGI blobs, or in the case of Bug/Too, both. Strangely, of all of those titles you listed, I liked the music the most in all of them. I was just listening to the Clockwork Knight vocal album last week, and the Weevil Dead music in Bug Too is something I can put on a loop for twenty minutes.
Don't forget the score system in Keio 2. Basically doing a good deed raises your score, but rampaging around and breaking everything gets you minus points. If you die you also get minus points. A higher score unlocks more bonus images, while a negative score unlocks hints and tips. You can therefore go for both a positive and a negative high score if you want. The bonus game with the kappa (the frog you use as a trampoline) is littered with both plus and minus points, although the plus points are usually on the top.