Well, after finishing the game, I can safely say that this is the best version of Rayman 1. The game is still challenging, but fun, especially when you really get a hang of the game's mechanics. For example, it took me a long time to get used to the new gold rings, but when I did, I thought they were an incredibly fun gimmick. Another thing I had to get used to was having access to all of Rayman's abilities from the start, but that was easy enough. I also noticed that the jump height felt slightly higher than the original, and I don't think you could glide indefinitely in the original either, but these are all good changes.
I also appreciate the sheer amount of extra content. An entire new world, new boss fights, Magician's Challenges, and especially the new Bzzit levels (as I thought he was completely underutilised in the original game). Not to mention the "final" boss, which I thought was a massive improvement over the original that actually left my heart pumping when I finally beat it. I thought the real final boss was a little easier, but that might be because I had some extra health and about 50 lives by the time I went into it. As for the other bosses, they were all great improvements to the originals as well. I'd like to highlight Mr. Skops, who went from one of the easiest bosses in the original to one of the most difficult, although I was disappointed by the lack of the chase segment that happened beforehand in the original.
My criticisms towards the game are mostly ones that I had with the original. Even though the levels have been redesigned, there is still some hint of the old Rayman BS in some of the levels, and I felt like the later levels increased in difficulty a bit too drastically compared to the first half of the game. Still, the game was balanced enough that I never really felt like it was unfair like the first game. Another criticism I have is with the changing of some certain sprites, but that's a discussion that has already been had by others before, and it doesn't bother me too much.
Overall, I'd give this game a 9/10. It's a fairly faithful remake which still has enough amazing extra content to make the original game seem pointless to own for all but comparative purposes.