I'm just annoyed at how most of the fans think it's the messiah of Sonic games.
I don't think that's the case, it's more like a vocal minority. I happen to be part of it *cough*, but the vast majority of Sonic players never even played it, and even from the ones who did (just ask our own GreenGibbon!) and a good number the ones who later discovered it via emulation/PC port came away considerably less impressed. It does have enduring mystique thanks to superficial values like the anime opening and ending, Metal Sonic, and the aforementioned fact that nobody played it.
True, but the time travel feature is difficult to use in that you have to maintain a high momentum for a few seconds to take into effect, at which point you have probably meet another obstical causing you to slow down. I guess there's always the level select cheat.
The time travel is supposed to be difficult to use. That's why the levels are built the way they are. You're supposed to roam all over them, exploring, experimenting, and playing around trying to find good places to warp (the very existance of the Future stage variations just goes to show that you were just intended to play around in them, since they are 100% optional). It's designed entirely contrary to the Sonic 2 (and moreso 3) ideology, where the emphasis was placed more on speed (rather than the careful control over your speed) and easy loops.
Sonic CD is one of those cases where you get more out of it the more you put in, but if you retreat to cheat codes before you've discovered how to enjoy the game then you've missed the point entirely.