I still actively play Blue and Silver. I'd probably still play Yellow (Despite it being my least favourite game out of the 3), but i've lost it somewhere.
On my physical Blue and Silver carts i'm using Silver to train up some of Blue's Pokémon so that I have an array of different Pokémon all at the same level (Ideal for Stadium).
On the Blue rom i'm playing atm i'm trying to train up a Lv 40+ team before I fight Brock. As you can imagine, training Lv 30+ Pokémon in Viridian Forest is highly time consuming haha. I've been on it all day and i've not yet managed to level any of them up to Lv 40. I'm stopping them all evolving until they learn their final moves/the last moves I want them to learn so it could take a while to get them all done (Especially Charmander who doesn't learn his final move Fire Spin until Lv 48!).
Team so far:
Charmander: Level 35 (Raising to: Level 48)
Ember, Rage, Slash, Scatch (Keeping Scratch until he learns Fire Spin purely because it has 35 PP and when you're fighting level 3-5 Pokémon you need all the exp you can get)
Spearow: Level 28 (Raising to: Level 29)
Mirror Move, Peck, Leer, Fury Attack
Nidoran (M): Level 36 (Raising to: Level 43)
Horn Drill, Fury Attack, Poison Sting, Horn Attack
Pikachu: Level 29 (Raising to: Level 43)
Swift, Thundershock, Quick Attack, Thunder Wave
As you can see i've still got a fair bit of work to do. I'll let them evolve once they reach the levels i've listed and hopefully I should have a pretty solid team. Also wanting a Magikarp once Brock's out of the way, so that I can add a Gyarados to the roster. Or I may just skip Brock and go level it up before I fight him. It may seem harsh but watching his team crumble to Hyper Beam will be absolutely priceless :D
Do the hard work now and reap the benefits later on in the game, I say!