Turok: Rage Wars (Bit Managers/Acclaim Entertainment, 1999)
I've seen this game on some other people's "best of" lists, and I have to assume that was because of the fantastic music and decent graphics rather than the awful gameplay. This first level goes on for ages without ever changing, and none of the enemies pose any threat as long as you let them come to you and then stab them. You have other weapons, but the knife is a OHKO and there's no reason to use them. The second level's clever idea to shake things up is to become an auto-scroller, which does not help.
Turok 2: Seeds of Evil (Bit Managers/Acclaim Entertainment, 1998)
The first Turok to release on GBC had more varied backgrounds, but worse music and abysmal gameplay. The humans here all look the same, but some of them are randomly hostile and you can't fight back. Eventually you'll make it into a warehouse with grey dinosaur people, who are always hostile but still immune to damage. If you die there, you go all the way back to the beginning of the level. It's awful, and I don't understand how anyone thought that design was okay.
Turok 3: Shadow of Oblivion (Bit Managers/Acclaim Entertainment, 2000)
It reuses a ton of assets from the first game and inherits its problem with forcing an extremely slow pace. If you try to go quickly at all, you will take damage. The only way to be safe is to freeze every time you see an enemy start moving and hit them as they come to you. The second level also throws in pitfall traps to really emphasize that you're meant to walk very slowly.
Tweenies: Doodles' Bones (Tiertex/BBC Multimedia, 2001)
It's a Tiertex game, so it doesn't start.
Tweety's High-Flying Adventure (Kemco, 2000)
A puzzle platformer where you need to beat up Sylvester in order to beat each level. The graphics are terrible, but it was modern enough to have a tutorial and the gameplay is at least fairly original.
Uchuu Nin Tanaka Tarou de RPG Tsukuru GB2 (Enterbrain, 2001)
Another RPG Maker for GBC, but now with a couple of basic example RPGs built in. I'm still not really sure why you'd want RPG Maker on a handheld with no way to transfer your work to anyone else.
Ultimate Fighting Championship (Fluid Studios/Crave Entertainment, 2000)
A fighting game has movement towards and away from the camera even though it's really hard to tell which plane your fighter is in and using that movement results in a lot of comical missed punches and kicks. Health regenerates slowly for both you and your opponent and none of your attacks do much damage. The only way I could make any real mark was to press A and B together to tackle my opponent and then punch him to death while pinned. I wouldn't call that strategy very fun.
Ultimate Paintball (Morning Start Multimedia/Majesco, 2000)
Despite the name, this has almost nothing to do with paintball and would be better thought of as a collection of randomly triggered shooting gallery minigames. It's boring.