Gameboy games, on the other hand, are practically free when it comes to all but the rarest of carts, which is why the price point needs to be kind of on the low side. Also, talk about not holding up.... black and white games meant to be played on a tiny little green screen. Portable games don't hold up at all imo because most of them (not all) are downgraded ports of home console games. I think the entire Gameboy line, from the original to the gba, might have 20 games still worth playing. Most are Zeldas and Metroids with a Castlevania or two thrown in.
I definitely do not agree with this. There are plenty of great games from the GB-GBA that hold up, from every genre. You also have some arcade remakes that have expanded on their gameplay and in a lot of cases improved on the console viability of those games. Look at DK, Burgertime Deluxe, Qbert for the GB. Amazing improvements that have higher production values than the originals. Then there are the hidden gems like Mercenary Force, ZAS, Mole Mania, Revenge of the Gator, Shantae, Trip World, Gargoyle's Quest, Survival Kids...I can go on, and that's just GB titles! IMO the GB is one of the greatest systems with a library of titles that bridge the gap between arcade and console games.
For GBA, yes you have the standard pedestrian titles, but there are also a lot of great hidden gems as well. Before speaking about those let me mention the Castlevania's; here you have 3 awesome follow-ups to SOTN, high quality titles with great level design and artwork. If you're a metroidvania fan, these titles are vital to the fandom. Heck even Metroid Zero and Fusion are worth mentioning since they carry on the series rather than just porting, 'cause lets be honest there are a lot of SNES ports on the system from the Marios to Final Fantasy's.
Now I digress, other GBA titles worth mentioning: Sword of Mana - awesome remake/reinvisioning of Final Fantasy Adventure (SoM1), Sigma Star Saga, Astro Boy, Gradius Galaxies, Boktai (very clever game using a light sensor), Mario vs DK, Pokemon Pinball (actually pretty decent and a fun "catch-em-all" spin on the franchaise), Pinball of the Dead, Mother 3, Steel Empire..again I can go on and on.
From these lists alone, there are many more titles that hold up much more than the handful of N64 "good titles". But again YMMV. I suggest giving the GB -> GBA titles a chance.