I have played the first game up to completion for now.

The word that would come to mind : chill.
It's not a very hard game (albeit not easy either) so it doesn't take too much brain power, it's fun to figure out where are the hidden gems using the level design and the artistic direction are not only pretty good, but works very well on a relatively low end computer.

Bad points for me : Collecting gems feels incredibly useless, and that's what you spend most of your time doing, it's not hard, the remake even incorporate a help from the little fly who follows you, but just collecting the one that are right beside the player is mind numbing.
The bosses are a problem too, I like them in concept, the idea of combining platforming, running and attacking for each of them is good but they're so easy you end up asking yourself "what's the point".
This is what i asked myself when i finished the first game actually. I have a lot of hope for the second and third one, i know they alternate the gameplay in those, just like in the crash bandicoot trilogy so I'm waiting for now.
It was still pretty fun and i can recommend it already for the 3D platformer lover.