Jankyuusei: Cosplay Paradise (elf, 2001)
This seemed to be a VN about forming a cosplay club that's all girls except for you and where only they do any cosplaying, which is at least a bit pervy. Its sudden decision to become a mahjong game partway in makes a lot more sense now that I know that "jankyuu" is a combination of mahjong and pachinko. I didn't get much more out of it because, surprisingly and despite the simple sentence I took a screenshot of, this game has the least accessible Japanese of anything I've seen so far. Might've been able to get through it with time and a dictionary, but it seemed bad and there are still nine more games to play!
Janosch: Das Grosse Panama-Spiel (NEON Software GmbH/Infogrames, 1999)
After the least accessible Japanese game comes the most accessible German game, because there isn't actually any German in it. It's an adventure game where all the characters communicate through textboxes full of pictures and arrows, which still aren't always that easy to understand. The music is truly dreadful because whoever wrote it went for some really complex pieces with multiple instruments doing their own thing, but it just doesn't blend together at all.
KRTL: Jay und Die Spielzeugdiebe (Eclipse Entertainment/THQ, 2000)
Character platformer apparently drawn by a five year old about a lion who shouts "GRR" to attack. This goes even further than not having any German by omitting any attempt to communicate at all. I don't know what this lion's deal is.
Jeff Gordon XS Racing (Natsume/ASC Games, 1999)
Despite the Jeff Gordon license, it's actually a futuristic Outrun-ish racer that has nothing to do with NASCAR except for its boring oval tracks. There are some jumps in the tracks that don't add anything and they claim you're going 350 MPH, but otherwise there's nothing remarkable about it.
Jeremy McGrath Supercross 2000 (M4 Entertainment/Acclaim Sports, 2000)
This one makes me sad because the racing part of it is really good. It's a fairly simple overhead bike racer, but the tracks are fun and the AI is balanced well enough to keep the pressure up without feeling unfair. Unfortunately, it makes constant motorcycle noises that sound like a jammed blender. It's horrific, and it only gets worse if you bump in to anything. It would've been another game to come back and finish if only they'd had even passable sound design.
Jet de Go!: Let's go by Airliner (Altron, 2000)
The Train de Go people made a flight sim for GBC, apparently. It's as serious of a sim as you'd expect from them, but I feel like most of the fun of a flight sim is lost when you're on a system that can't render the ground in any meaningful way. You're just sort of flying in to a void and adjusting your path or speed every now and then.
Jim Henson's Bear in the Big Blue House (Ubisoft, 2001)
Now here's a show I hadn't thought about in 20 years. The game has you go between rooms and play bad minigames. There's not much more to it than that.
Jim Henson's Muppets (Tarantula Studios/Take 2 Interactive, 2000)
Character platformer starring Kermit where you can time travel to a bunch of different periods and places. You can shoot paper airplanes that don't seem to have any impact at all on enemies. That's realistic, but it's also pointless and not fun.
Jimmy White's Cue Ball (Vicarious Visions/Vatical Entertainment, 2000)
I don't like pool in real life, so you can probably imagine how much I enjoy it with finnicky GBC controls and some ass I've never heard of saying "hurry up!" before all of my turns and "patience, master at work" during all of his. Lemme tell you where to put that cue ball, Jimmy.
Jinsei Game: Tomodachi Takusan Tsukuruyo! (Alpha Unit/Takara, 1999)
The original Jinsei Game came up earlier. "Let's make lots of friends" seems to be a sequel with more life stages and a focus on adding your friends to the game as player characters. That's a pretty neat idea, and playing that way is probably necessary to enjoy what's otherwise a lot of RNG nonsense. This is one I might come back to depending on what the list looks like at the end - I'm interested in where it goes and it's probably not that long, but I saw some heavy RNG even in the first four turns.