Konami time: I recently picked up Gradius II for the SCD. Despite owning the arcade game on the Saturn, the subtle changes made to the port here are quite admirable:
1) the shot limit is increased, which makes recoveries and the beginning of the game easier
2) Ripple lasers are more accurate and effective than the arcade original
3) Moais shoot more rings and can shoot offscreen, but are slower in speed
4) new stage is excellent
I haven't gotten farther than the high-speed stage, but I've been told that the zub rush at the end is more difficult, the boss rush is a mite more manageable, and the Gun Wall is more tame on account of the weaker hardware. So some things have been made trickier, whereas others have been lightened up because of running off of PCE processors. I think that overall is not too bad, since the game is plenty hard as-is. I don't know if it will convince me to let go of my Saturn collection any time soon.
I also cleared the first loop of Detana!! Twinbee, which is also another port that can boast of highly-polished Konami fine-tuning: e.g. slightly more forgiving, tweaked hitboxes, and designed well for 4:3 ratio
Final levels are very tricky, especially with all those damn bells flying everywhere.