It really made him look like he was the ultimate pokemon in the episodes that they were in Sabrina's gym. If Kadabra could do that in the games, there would be no need to carry another 5. Also Ghosts weren't the only ones that had an advantage, a bug type also has advantage over Psycic.
Yeah, but remember the trashy bug types from the earliest generations? You`re normally not fighting with them, and won`t want to train them simply for the Sabrina fight. I always favored the ghost pokemon, like Gengar, and they`re also useful for other battles as well.
But with Sabrina and Kadabra, you made a point. Although Kadabra IS (was and still remains) avery useful and strong Pokemon.
Actually Alakazam can bascically handle the E4 in the first series Red/Blue/Yellow by himself after lvl 60ish. And Bug and Ghost may have an advantage but it's their second type of Poison that allows Psychic to out match them. Gengar is ghost poison, and I can't even think of a decent bug pokemon from first gen. Pinsir...
Scyther was always under powered, they should of made him stronger so people take bug type seriously. Everyone liked Scyther but it was never as good as it looked.