Dragon Quest Monsters, i always thought they killed pokemon even back on gameboy color
DQM 1 on gameboy color is the first and i'll say it's got a WAY better breeding system than pokemon, where newborn monsters can be stronger than both parents with moves from both, and higher level cap
maps are randomly generated, other than the final floor of each gate with a boss fight, makes reference to basically DQ all the way up to 6 (the main character is Terry from DQ6) but you can play without knowing them (I did, not having played DQ 1-6, DQ monsters was my first dragon quest game)
DQM 2 on GBC is two game versions, one has you play Tara, and another as cobi, brother and sister with a decent bit of different plot and areas, sorta pokemon in terms of trading monsters, but you also need both games to access all areas in both games (using keys that can be traded between games)
if emulating you can just use a gameshark code or etc to access stuff
mGBA can game link with both games side by side also if you wanna do it the right way lol
both games are remade on 3DS (very different using newer DQM game mechanics) both in japanese, with translated versions out there online.
DQM3 dark prince is on PC and switch... but this game literally looks like a 3ds game (like they ported a cancelled 3DS game) if you can get past that, it's quite good as the most recent DQM game, lots of monsters and breeding still, and a quite interesting story (prequel to DQ4, you play the main antagonist before that games events)
anyways other than dragon quest, I HIGHLY recommend CASSETTE BEASTS
like, it's so many things better than pokemon idk where to start,
being able to FREELY switch moves (called stickers in game) between other beasts,
some moves are passive too like, start with a random move, use the same move twice, other random effects and etc.
you can use a lot of moves on one beast, like 12 in total if i recall?
but no the major highlight is the FUSION system, where 2 beasts fuse together in battle to make a bigger monster, the form and appearance vary by the two you used (there's like 20,000 combinations)
it also merges the moves of BOTH monsters into one, giving you really wild setups and multi-type crazyness,.
and then the game has customizable level scaling, like, you want every enemy to be the same level as you, put it all the way up, you want them to just stay at default levels , put it off entirely, it has a slider to so you can do more/less level scaling, it's a huge game changer
and AI difficulty, from pick moves entirely random, to actuall serious thought of buffs and effects and such (i couldn't play max difficulty they're too smart, unless you do some really cheesy crap)
the type matching up is very different from pokemon, which elemental reactions like, fire against plastic, which causes pollution (poison to everyone in the fight) i forget the rest of the reactions the game shows a crapton of them.
oh also the game is 2 player LOCAL CO-OP and very well done, both players control one of the two characters, rather than p1 controlling two alone, and even outside battle they can run around and pick up stuff! you can play the entire main story this way!
there's ONLINE play but, sadly not the same as above really just for trade and versus battle and raid bosses, not playing through story together.
this game literally made me stop playing pokemon entirely, because why do i want an inferior game, and even recent pokemon games just are pretty terrible.