My top 3 favorites.
1. Team Fortress 2, this game really marked me as an steam player and fps player like i said in many other posts i made and commented, has so many good classes to choose, each one requiring different strategies and skill to be played correctly, even if i am not really the best player in this game, hell it doens't matter, it really entertained me when i first downloaded the game from steam in like june 2017, thanks to gmod or garry's mod, i still don't regret my first time downloading it, recommended, also it might have some toxic people you will have to deal with but, you can know nice people too, i recommend it and it's also free but is a freemium that means has buyable items, but still, very good.
2. Contra (NES), i played it recently in the nestopia emulator, and i enjoyed it, a fun run n' gun game, enough said.
3. Pokémon Red, Blue and Yellow, this game really needs mention of how enjoyable it is and for being the first pokémon game i have ever finished alone (in a emulator of course haha), i do understand gen 1 is overrated as hell and has some flaws but hey, it's gen 1, of course it will be overrated and have flaws, defects, bugs and glitches, but even if it had completed 20 years, it's still played today, and it definitely deserves the love it gets, even if i enjoyed fr/lg, i
don't think it will be enough to say it's better than the originals, i liked it but is just not enough to make say it's better , but yeah.
Honorable mentions are counter-strike 1.6, super mario world, team fortress classic (yeah, i had played it too, not as enjoyable as tf2, but at least it exists), donkey kong country, super smash bros. melee, super mario bros. (nes), counter-strike source, counter-strike global offensive (yeah, those 2 i mentioned i just downloaded them non-steam, like counter-strike 1.6), gta san andreas and gta iv.
As of now, i have no least favorite, i might edit this post when i think about my 3 least favorite games.
Sorry for the long text, it's because i felt it was necessary to put all of my feelings about my 3 favorite games.