I'm going with 7 this time because past that point my picks become notably harder to justify, but I want to point out that I was able to find over 25 games I played from 2004 despite missing literally all the biggest names like Halo, Half-Life, WoW, GTA, MGS, etc. Insane year.
1. Touhou Eiyashou ~ Imperishable Night
To date, still the most ambitious and fully-featured Touhou game, essentially the "late DS Pokemon" of the series before future entries deliberately scaled back and focused on one-off gimmicks. A large cast of playable characters with interesting shot types, a whopping 222 Spell Cards, nine different bosses, and the addictive Spell Practice Mode which almost feels like a whole game within a game are just some of its more prominent features. The soundtrack is great from start to finish, and immediately sets a distinct mood the moment Ghostly Eyes begins as you enter the first stage. I've heard it described as "nocturnal-psychedelic", which has always stuck with me. I consider Imperishable Night the best entry point to the series, and I've seen it hailed as a great entry point to the genre as a whole due to doing a good job teaching fundamentals while having a lot of difficulty options.
2. Metroid: Zero Mission
Great Metroid for both beginners and experts, though it falters a bit in the midrange. I maintain that the art direction of bubbly terrain and brightly colored outlines is ugly and hurts the atmosphere compared to Super or Fusion, and that the work put into the Chozodia epilogue would have been way better spent on adding a new area to the main game, like Maridia. But the gameplay is excellent and it's impressive how much they were able to rehabilitate level design that was originally a bunch of identical shafts and corridors. Frankly, this is a 9/10 game, and it's astounding that it's built so faithfully on the 3/10 foundation of the original Metroid, even if the final product bears almost no resemblance to its inspiration beyond the layout.
3. The Legend of Zelda: The Minish Cap
A little bit of "you can tell this wasn't made by Nintendo" weirdness, mostly in a negative way like having missable and post-game items, but it's one of the better 2D Zeldas regardless, only surpassed by ALBW and LA remake. It has a lot of cool ideas that are unique to it, and Hyrule Town is easily the best 2D Zelda town ever. Also probably the most famous pixel art on GBA, so many indie games copy Minish Cap's trees...
4. Paper Mario: The Thousand-Year Door
Thanks to the remake I think we all know at this point why this one can be tedious, but also why it's really damn cool.
5. Donkey Kong: Jungle Beat
When they talk about violent video games, this is what they mean. You really feel like a gorilla brutally beating a legless pig.
6. Sly 2: Band of Thieves
The weakest of the Sly trilogy, but still a solid platformer. Probably the most "gameplay first" one, though also with the least interesting level design due to a larger reliance on setting missions in the hub worlds. Unlike the others, it rarely interjects with alternate gameplay segments and minigames, being very focused on the core movesets of the three main characters. Unfortunately, it also runs rather long and gets very repetitive, with much more simplistic missions in comparison to Sly 3 and a lot of more formulaic "okay, it's the start of a new episode, go take pictures of the bad guy again" stuff.
7. Metroid Prime 2: Echoes
The coolest and most original Metroid Prime. Many new abilities that aren't in any other game! A distinct aesthetic identity due to the general absence of Chozo architecture and technology! Combat that's a smidge less bad than the other two! Wish 2/3 of the game wasn't spent in drab wastelands and dark worlds, also wish it wasn't a pain to navigate and obsessed with keys. The ending is probably cool, but I just really wasn't feeling yet another key hunt after getting the Light Suit, so it's the only game in the trilogy I've never quite finished. One of those sequels that's maybe a bit too ambitious for its own good, like Banjo-Tooie, but I can't help but respect its complexity.
Honorable mentions to:
Fire Emblem: The Sacred Stones, which seems really good especially in comparison to all the other GBA SRPGs I experienced it back to back with, but I've never played beyond the first few levels
Pokemon Emerald and Pikmin 2, two very formative games in my childhood, but neither of which I would really call "good"
The SpongeBob Movie Game, which is kind of like a funny kaizo hack of Battle for Bikini Bottom, way too scuffed to include in good conscience due to the shit you have to go through to meet the token requirements alone, but it has some of the better challenging 3D platforming I've seen
Four Swords Adventures, which is neat
