Considering not just the ramps by themselves, but how they integrate with the game, here are some thoughts:

Creech: While the Long Bowl ramp rightly gets all of the focus, the right ramp is also great. Hitting that ramp multiple times and activating Snack Attack and then shooting the scoop is one of the best single ramp combos I know of. Very original between those 2 (really three) ramps.

SM venom ramp is great and very different and leads to great combos to the other 2 ramps

Stern ST: great flowing ramps with amazing side warp ramp combos

WH2O is all about ramps and they are very original

TOM has 3 very nice ramps including the Left Orbit/Ramp. Comboing the center ramp to the right orbit to the Trap Door is amazing. The right ramp is challenging and has the magnet diverter to the left flipper for right ramp combos.

DI has very very smooth flowing ramps that tie into the overall flow of the game. Significant mode use on ramp shot and use of ramps to get from one flipper to the other or keep the ball away from the magnets on EMP mode. Adjusting/timing your shot on the upper right flipper to not to hit the side ramp and instead collect the SIM card

Batman Forever is all ramps and wire forms. It has 4 ramps (one is a small but fun mini orbit ramp) with a Batarang ramp combo maneuver similar to STTNG.

LOTR mentioned previously for the left ramp but also the challenging center ramp ball catch in the ring.