3D Altered Beast is the 3rd game of the Sega 3D Classics line I've played.
3D Sonic the Hedgehog was possibly the best way to play that game. 3D Streets of Rage is probably the best way to play that game. 3D Hang-On, 3D Space Harrier, 3D Galaxy Force 2 - probably the best way to play those games outside of the arcade. Play all of those games, they are fantastic. I didn't even like Hang-On and Space Harrier, and the 3D versions have swayed me - I actually really enjoy them here.
3D Altered Beast isn't quite so definitive. For a start, this is a reworking of the Mega-Drive game. Why? There's literally nothing to recommend it over the Arcade version. Secondly, and I think this is important - although this is possibly the best way to play Altered Beast, it is, very notably, still a shit game.
Altered Beast is a terrible, terrible beat-em up. There's not much you can do to save it from the title. They've added a 'random form' mode, which is nice, but the issue is that most of the bosses are really designed around the form use on their level anyway - taking on the stage 2 boss with anything other than dragon is nigh on impossible without losing lives (for the record, I did this mode on my run and got Wolf, Wolf, Dragon, Bear, Bear on the 5 levels). It also accentuates how unbalanced they are. Tiger, the last form, is without a doubt the worst. Dragon is totally broken. The other two are OK. The gameplay is still no less boring, the variety lacking and there's no reason to really play it still.
The 3D effect here is also the worst in the 3D Classics series - not through a lack of effort mind, but because Altered Beast is a flat,boring game visually. Flat backgrounds, no parallax - it's just not a good game to remake in 3D. It's not a notable feature for this game, and it's already a crap game to begin with.
There are exactly 3 positive things I have to say about Altered Beast.
1. This is hilarious:
https://www.youtube.com/watch?v=EOQcnliEjXM
2. So is this:
https://www.youtube.com/watch?v=W_9VsnQJLjA
3. Literally every pose the Bear-Man makes is also hilarious:

May favourite is the 3rd one. He's like 'I don't give a damn, I'm a motherfuckin' bear!'
Only pick up 3D Altered Beast is only worth it if you want to get the entire set of 3D Classics. Otherwise, avoid. It's not worth it to own a(nother) copy of Altered Beast.