well ive got a few options, im only going to put ones ive actually played down since i can give a better guide into what your stepping into:
pokemon rejuvenation: easily the most difficult pokemon game ive played but one that i really enjoyed none the less( definitely one to pick if you want a challenge) you have the choice of 24 starters from all the mainline games and all pokemon up to generation 8 throughout your playthrough, no fakemon( well one, but no spoilers!) and for the rare occasion you actually have a difficulty setting, easy, normal and intense. but dont be fooled, even on easy all gymleaders will have at least 4 pokemon, normal and intense will have 6( even the first gym leader) and it took me a long time grinding in the main city to even beat the first leader as well as some hectic strategy and luck, stage effects are a big thing in rejuv and all gym leaders will use them very well(you should abuse the effects as well) there is also no overleveling here as at some point your pokemon will stop at a certain badge level, other than that a fantastic story, areas have a wide pokemon variety, and special one time only pokemon can also be obtained, shiny odds are also wayyyyyyy higher in rejuv(a 1/100) chance meaning you can easily have a full shiny team before the first gym leader( and them watch them all faint when she kicks your ass the first time) ev and to some extent iv training is sometimes necessary to have a easier time, as later on you will be versing full iv and ev trained pokemon. definitely the most satisfying pokemon game once you beat a gym leader, only downsides for the game itself is that the difficulty can feel overbearing at times, it would be fine if you and the gym leader have fair sides all and all, but you cant even ev easily train in the beginning( you need to buy ev training cards) besides iv training( you cant get a ditto till the 6 badge or the destiny knot ) and all gym leaders have a ace move that you can never learn and they are kinda broken( poison move that is super effective on steel types and has 50% chance to poison :() or kugas move that ALWAYS critical hits) so at times it can definitely feel unfair. but still great game
pokemon insurgence: definitely easier than rejuv but can still kick your ass, kinda fakemon since its 150 different variety of other pokemon ( a ghost dark type charmander for example ) which you'll encounter at least one per new area, these delta pokemon are super interesting actually and can give new spins on old pokemon( a muk made out of sand? or how about a electric ice type gallade!) your get a choice of three starters( all delta pokemon) or if deltas arent your thing you can get a eevee as well ( still a special eevee! but no spoilers!) stage effects are still a thing here but to a less degree( which i actually prefer sometimes) story itself is also very good but not as good a rejuv, ev and iv trainng are still needed here but thankfully are way easier to get and you can easily level up your mons in the process, shiny odds are still pretty standard here sadly but they are some boasted rates here and there, leader are based around a theme rather than a single typing which can be pretty cool, no overleveing as well here,and new areas are also have a wide variety of pokemon ( non deltas) to choose from, definitely a happy medium between rejev and uranium
pokemon uranium: much easier than insurgence and rejuv with some slight difficult learning curves here and there but i doubt you'll be losing more than twice to any trainer, a slightly harder but still normal pokemon game all and all, fakemon? bro this game doesnt have any normal pokemon( besides one but again no spoilers! ) the fakemon are pretty interesting here actually and definitely have there own sense and charm with some really cool typings!, the game also introduces a whole new typing as well which very cool( radiation that is super effective against everything but is also weak to everything!) stage effects are unchanged from the normal pokemon games, you dont have to care about ev or iv training here, just be somewhat smart with some decent strategy and you'll be fine, the story is alright but nothing to write home about but does have some interesting plot elements not seen in alot of pokemon games, im not sure if the new pokemon have shinies and i didnt encounter any on my playthrough, leaders are the standard typing, pokemon variety is pretty decent just dont be comparing rejuv which has 800 pokemon to work with while uranium has around a quarter of available fakemon, great game if you feel bored of the standard roms and wanna see something a little different.
and that my list! in summary: pick rejuv if you want difficulty and satisfying moment( and your a bit a of a pain lover on intense difficulty). pick uranium if you want the standard pokemon with a twist of fakemon and a different story, and pick insurgense if you want a mix of the two. and a shout out to pokemon snakewood cause its the next romhack im going to play because zombies.
have fun!
