I used to think Aeroblasters was a great game, up to stage 3 anyway. After that, the later stages are no fun because of the gravity effects.
The gravity effects only add to the challenge
.
Spriggan is a good choice, and I love it, but I'm surprised folks here haven't pointed out that while it is a rock-solid game, it lacks the novelty of
GOD PANIC.
The same can be said for Raiden, which lacks the novelty of
Hany in the Sky.
That said, if you really like shooters, definitely get Spriggan.