>>42124987Ghetsis's team is not meant to be thematically consistent. It is meant to show off some really good Gen V Pokemon.
Bouffalant, a Normal-type, only has one weakness and it has great attack and a good ability in Reckless.
Cofagrigus has great bulk, a good defensive typing with two immunities, and an ability that screws over contact users.
Seismitoad only has one weakness and can power itself with Swift Swim.
Bisharp, at the time this game was made, had two double resists (Dark and Ghost, before the Steel nerf), 7 resists, two immunities, and was only hit neutrally by 3 types (Bug, Water, and Electric).
Eelektross had virtually no weakness thanks to Levitate on top of decent offensive stats.
And Hydreigon is this game's pseudo/late bloomer.
Ghetsis chose a pretty good team with the limited options he had, which goes hand in hand with his philosophy of wanting the best Pokemon for himself.