Games I wish had modern sequels? Here's my list, just to name a few:
Ninja Golf (Atari 7800)
Cybermorph/Battlemorph (Atari Jaguar/Jag CD)
Todd's Adventures in Slime World (Atari Lynx/Genesis)
Roadkill (Xbox/PS2/GC)
Mind Strike (Intellivsion ECS)
Iron Soldier series (Atari Jaguar, Nuon/PS1)
Sticky Balls (Gizmondo)
T-Mek (32X, Arcade)
I-War (Jaguar)
Outlander (Genesis)