I tend to be far more critical of platformers than other games. Highly regarded games like Rochard fall flat on me. There is a very particular reason for this. Many so-called platformers actually aren't good at the things that define platformers. Those things are timing and precision.
Many developers and gamers seem to think that being a platformer means having a jump button. A true platformer is one where the player is tasked with moving from one place to another with the primary difficulty coming from the precise timing and execution of their actions, mostly movement actions. There are many games out there that call themselves platformers, or some type of platformer hybrid, that really are not.
The puzzle-platformer is like a platformer, but with much more critical thinking involved. My most recent experience with this genre is when I played the demo for Rochard. Don't get me wrong, I do like puzzle-platformers, but not because they're platformers. In fact, I usually dislike the platforming, because it's often terrible.
Most puzzle-platformers spend far too much time developing the puzzles and no time developing the platforming. As a result, they'll often end up with a super floaty jump and nothing else. If there was a simple heuristic to measure how good the platforming in a game is, I'd have to go with the floatiness of the jump. The floatier the jump, the worse the platforming.
On the opposite end of the puzzle-platformer is the action-platformer. You can pretty much take everything from the previous section and replace 'puzzles' with 'killing things'.
There are two ends of this spectrum. At one end are your action games that have jump button. This would be like Devil May Cry. Yes, you jump. You're even sometimes asked to jump over or across things. However, jumping and movement are not your primary obstacle to progression.
On the other end, I'd place Mega Man or Ghosts n' Goblins. In these games, the enemies serve as timing/coordination challenges. While there are tons of enemies to kill, you also don't necessarily have to kill them. Uncharted 1 starts more towards the platformer side of the spectrum and becomes more of an action game as it goes on. This was one of my main complaints about the game.
I've found that a common way to measure where a game falls on this scale is how easy the enemies are to kill. If the enemies are easily killed, it falls more to the platformer side. If the enemies are harder to kill, it falls more to the action game side.
I love action-platformers, no matter where they fall on the spectrum. I'm playing Uncharted 3 right now and it's totally awesome. And really, when you get down to it, Uncharted 3 has action, platforming, puzzles, and a great story. It's the whole package.
The degree to which a game is a platformer comes from the timing and precision required for your movement actions. Enemies and puzzles can be added to the game to round out the gameplay, but can sometimes pull the focus away from the platforming. I'd really like it if more games were true platformers. I think many developers are afraid to do that, however, because of the obvious Mario comparison.