Swampert is 4x weak to Grass so I don't see the point about worrying about 4x weaknesses.
See here's the thing though - the only other water/ground combo we had was Quagsire, Whiscash, Gastrodon, and Seismitoad. Water/flying has Gyarados, Swanna, Pelipper, and Mantine lines. If you wanna say before 4th gen, that still leaves 2 water/ground vs 3 water/flying.
Throw in the 4x weaknesses - grass and electric - and it becomes a whole different ballgame. Before gen 4, we had Pikachu, Plusle/Minun, Electrike, Magnemite, Voltorb, and Chinchou vs Treecko, Seedot, Lotad, Shroomish, Cacne, Oddish, Lileep, Tropius, and Roselia.
Taking into account which Pokemon are more common with trainers than others - Plusle/Minun, Seedot, etc vs Treecko, Pikachu, and Tropius - and how many of the STAB moves each can learn or usually has - Seedot not getting very many until it becomes a late-level Nuzleaf/Shiftry and Electrike only really getting Spark and Shock Wave - it's pretty safe to say Swampert had a slight advantage over Pelipper or Gyarados.
Plus we didn't have a grass-specialist as far as gyms/elite go.
I don't think we'll be getting a water/flying starter for a little while.