[twillight]

The optimal (meaning the least amount of pokemon) to have ALL the useful out-of-battle movesets (so this includes HMs, Dig, Teleport, what have you):
- Red: Slowbro + Farfetched (you don't need teleporting much in this one, the maps are adequately small, and Dig brings you close enough to the local hospital)
- Gen 2: ???
- Emerald: Seedot + Marill + anything that can fly + Abra/Ralts (Abra is a hard-to-cath option, but you have to level up Ralts if you go that route). I'm not entirely sure yet wether you need that teleport in this one yet. Extremly rare move in Emerald, it is.
- Platinum: Bidoof + Bibarel + Starly + Abra (teleport is helluva good in this one)
- X: You have a couple of options, the base can be collected pretty soon. Catch a Ralts for Flash and Teleport, and depending on what you want, you likely want it to be male, and evolve it all the way up, so it can learn Cut and Strength in addition, though this is not obligatory.
Also before the first gym you can catch a bidoof, what you'll upp to bibarel, and that can learn all kinds of stuff. It'll definitely be the one learning Surf and Waterfall, but you still need something that flies, and can learn at least 2 more move above that (and is available soon, and not post-game).
This thins down the list to 2 candidate: hawlucha, and aerodactyl. Pick any, and adjust your bibarel (and Ralts) accordingly. In the end you'll carry around 3 HM-slaves.