A good game, but not as good as the original.
The original game was just betting in pretty much every way, so I'll only go into the big differences.
Gameplay:
The new game focuses on the side scrolling / platforming aspect, with a couple flying levels. The original was much more varied. While the basic gameplay usually was either platforming or flying, the levels had enough variety to keep it interesting. In the new one, each level seems to be exactly the same, but with just a different background, and even those don't vary that much, which brings me to my next point:
Variety:
I feel this is the area where this game fails the hardest. The original was so good because of it's large variety of levels. You never felt like you were doing the same thing. The game even switched things up mid-level. One minute you're escaping a burning castle, and the next you're on a mine cart battling an evil train. It was incredible. All the levels in the new game feel exactly the same. They have slightly different backgrounds, but that's it. The personality from the original just isn't there.
Graphics:
This is another case where this game just doesn't quite do it. The graphics are technically alright, but they just lack the character of the original. I'd prefer cartoony sprites to pseudo cell shading any day. This should have been done in HD sprites. Also, the design is just way more boring than the original. The enemies, levels, etc, just seem bland.
Audio:
The only part of the audio in the new game that was really good was the first level.... because it was the same music as the first level of the first game. After that, it was all forgettable. I distinctly remember all the music from the first game. The creepy boss music, the silly mine cart music, it was all fantastic. This game just didn't quite get it.
Overall:
This game isn't bad, but I'm such a huge fan of the first one, and had such high expectations, that it might seem like I'm being a little harsh. But why shouldn't I be? They've had almost 20 years to perfect the strategy. They know what made the original great, and seem to have thrown most of those ideas away. This game is in no way bad, but it is disappointing. If you haven't ever played the original, then most of my complaints won't matter, and you'll most likely enjoy the game, but compared to the original, which I highly recommend, it falls flat.