ok people, here it is: a interactive ranking of pokemon type and ability combinations, both defensively and offensively.
you can order pokemon by their defensive rating, offensive rating and number of weaknesses.
the champion in the defensive ranking is shedinja, and the loser is aurorus.
the champion in the offensive ranking is mega lucario, and the loser is, well, any normal-type pokemon, with special honors to delcatty.
the champion in the lesser weaknesses ranking is eelektross (with 0), and the loser is tyranitar/terrakion/shiftry/lunatone/solrock/exeggutor (with 7).
have fun.
http://inf.ufrgs.br/~morprates/pokemon_ranking/ 