I believe Godai is supposed to be the first one with the Rising Forms because, if I remember correctly, they result after he got shocked by the defibrillators in the hospital the time he "died" (in the Mushroom Grongi storyline.) The electrical energy somehow affected the Henshin Belt/stone thingy in his gut.
The final battle between him and Daguba is really unique. I think what they were trying to convey is how utterly powerful each one had become, being able to just set the other on fire with a wave of their hands, so the only way they can really settle things is just with this all-out fist fight with no fancy stuff, just raw brutality. It's really not what you expect at that point I think, but it's really cool. And I like how Daguba looks sort of like Kuuga Ultimate Form, but is white, whereas the good guy is the one in black. Nice little reversal there.
I think where most people don't like the ending is the final episode itself, which has no fight whatsoever, and doesn't even mention Kuuga. It's sort of more about remembering Godai just for what a good guy he was, and not so much that he was a hero. It's an interesting twist, and like I've said before I think it fits the character and series very well. It's not as exciting as say, the end of
Kamen Rider Stronger, with the original 7 Riders back and kickin' ass, but what is?
As for other Kuuga stuff:
-there is an "episode #50", but it's a short, self-made parody of sorts, nothing really important to the story, but it's pretty funny.
-there's a TV-Kun video special, but it's also just a short thing with Kuuga fighting a new Grongi and mostly to show off Rising Mighty form.
-There was a TV Special that aired near the end of the series, mostly just a recap of everything up to the last few episodes before the end.
-The Kuuga "movie" is just a special edition of the first two episodes, which came out after the series ended. They change around music, sound effects and such (i.e. Daguba's voice is that of the guy who plays him at the end, not the creepy voice from the original episode #1), improve a few effects, and I think some scenes are longer, but otherwise nothing much new. I believe it was shown in theaters, at a special screening that also had a big interview with the cast (it's on the DVD with the episodes.)
So in other words, #49 is the last thing chronologically that's happened to Kuuga.