The Mummy (Konami, 2000)
Sure, it's probably a graphical bug that's causing poor Evelyn here to render as an interdimensional horror, but maybe it's just the mummy's curse! And maybe that curse is also why this is a crappy ladder action platformer. Seriously, did anyone actually like this genre?
The Mummy Returns (Game Brains/Universal Interactive, 2001)
This is a real contender for the worst game I've played so far. Not-Lara-Croft is trapped in an auto-runner where taking damage doesn't seem to matter, but being touched by the water(?) advancing from the edge of the screen causes an instant game over screen. It's very much in the Dragon's Lair school of "you didn't do exactly the right thing, so now you're dead and have to start all over" school of design.
Muteki Ou Tri-Zenon (Marvelous, 2001)
A mech strategy game. You might think it doesn't look too bad based on this screenshot, but what you're not seeing is that this board is actually 10x10 despite the fact that only 4.5 rows can fit on screen at any time. I don't know why they thought it was okay to make a strategy game you can't see 80% of, especially if it was going to use graphics this indistinct anyway, but that's what we have.
Nakayoshi Cooking Series 1: Oishii Cake Yasan and Pan Yasan (MTO, 2000/2001)
I didn't bother taking a screenshot of Pan because it's exactly the same game except more brown and all the references to cake have been replaced with bread. These seem to be slice-of-life games in which you collect recipes that you can then use in real life. Cooking based off instructions on a tiny GBC screen sounds pretty awful, but since using mobile screens for recipes is very common now, I suppose it was just ahead of its time.
Nakayoshi Cooking Series 3: Tanoshii Obentou and Dessert (MTO, 2001)
They changed the whole presentation to be a VN, but it's still the same concept. Now it's about bento and dessert.
Nakayoshi Cooking Series 5: Komugi-Chan no Cake o Tsukurou! (MTO, 2002)
Another graphical change, but also a return to cake. I don't have anything else to say about it.
Nakayoshi Pet Series 1: Kawaii Hamster and Usagi (MTO, 2000)
This weirdo wearing a hamster or rabbit hat shows up and gives you a rabbit or hamster, and then you have yet another tamagotchi-style game.