The reason why these typical green hill clones are so annoying is because they're the trope for the first zone and many projects don't make it past a one act demo. Honestly, I'd extend it past just tropical and into anything relating to flora or fauna for the first level as unoriginal. Be it tropical forests, grassy hills by the beach, woods etc. It's much more interesting just to shuffle the themes around; a late game green hill zone would be fun (and it would be cool to see how people modulate it to reflect the difficulty curve).
There's a fine line between having a style congruent to the classics and just plain unoriginality. A defining feature of the classic series is how each game evolved and mutated from the previous; Sonic 2 had Super sonic, Tails, two act zones, spindash; Sonic 3 had insta-shield, Knuckles, mid-act bosses; Sonic and Knuckles had playable Knuckles, Hyper Sonic, the first Super Sonic level. Following suit, fangames must also evolve to keep this old and maturing society interested. The need to pay homage and mimick every detail of the originals becomes lessened with each subsequent fangame that abides by them; originality and fresh, evolved ideas are vital in 2014 because as a community we have seen far too many fangames fall down the same formulaic routes.
That's not to say that having a tropical first zone, a Super Sonic last zone, or any zone mimicking a trope of the original games is an inherently bad thing, it's just when fangames do very little to push the boat out, however well made they are, they will ultimately be unsatisfying.