Your topic would be 10x better if you'd included what you thought was the best entrance sign before putting the question out to everyone else! It'll give your topic some substance and help people gain interest in the topic :]
One that sticks out in my mind is Goliath at SFMM. The 'rock' carving with the drop in the background is very iconic!
@Gerst: Not sure if you were being sarcastic when you called that sign artistic...
He's not kidding.
El Toro and Maverick's signage are nothing special. Rockin' Roller Coaster is really neat, and I honestly always like "Son of Beast's" empty box sign a ton.
From what I've ridden, Kraken at SeaWorld Orlando probably has the best coaster entrance. That entrance and the entire area really sets the mood for the ride.