Instant classic
Fly around and shoot stuff. Kill everything in sight. Sounds lame and boring, but when everything gets intense, like trying to dodge falling pillars and shoot robot giants at the same time, it's fun.
Graphics:
With the SuperFX chip, easily some of the best on the SNES. They are 3-D for crying out loud. How many 16-bit games can pull that off?
Sound:
With awesome voices (even though they are incoherent), great sound effects, and awesome music, nothing is wrong in the sound department.
Replay:
Find all the secrets and taking all the paths will keep you coming back to this one over and over.
Overall:
I actually can't think of one person I know who owns an SNES and not this game. Guess that should tell you people who don't own it a little something...