overall, i think the first generation was the best for non-gross/ugly/disgusting pokemon. the ones i don't like from the first gen are:
gloom
venonat
DIGLETT/DUGTRIO
exeggcute (there's NOTHING "cute" about them)
koffing/wheezing
TANGELA
mr. mime
jynx
2nd gen is where they started using baby pokemon, and for some reason, i don't like baby pokemon. i like my big strong charizard or dragonite, not a weird lookin' igglybuff.
here's a list of the pokemon i don't like from the 2nd gen:
all baby pokemon (except togepi, it's kinda cute)
sudowoodo
hoppip/skiploom/jumpluff (these aren't very good, why make hoppip evolve twice?!?)
sunkern/sunflora
wooper
wobbuffet
dunsparce
shuckle
swinub
ok, here's my 3rd gen list of disliked pokemon:
combusken
silcoon/cascoon
dustox
lotad/lombre/ludicolo
seedot/nuzleaf/shiftry
surskit
shroomish
slakoth/slaking
whismur
makuhita/hariyama
nospass
meditite
roselia
gulpin/swalot
spinda
castform
the regis (they seem like a lame legendary trio compared to the last two groups... i was disappointed...)
ok, 4th gen ^_^:
staravia
bidoof/bibarel
kricketot/kricketune
budew/roserade
rampardos/bastiodon (really like the lil guys, but i don't like what they evolve into)
BURMY AND WORMADAMS!! AHH!!
cherubi/cherrim (the purple looking one... what is that?!? lol, the petal blossom one is cool though)
ambipom (i almost died of laughter when i saw that one... LOL)
purugly (it sure IS ugly!!)
bronzor
baby pokemon
spiritomb
croagunk
magnezone/lickilicky/rhyperior/TANGROWTH/magmortar
gliscor
probopass/dusknior
froslass
regigigas
phione (manaphy's OK...)
whew, there's my list of what i think are the not-so-great pokemon
wow... kinda scary to look at... haha. well those are all of the pokemon that i think they could have spent more time on, or never put in the games/shows/etc. i'm really disappointed with magmortar. magmar is pretty sweet, and i feel like they ruined it with it's evo. anyways, i love all other pokemon, these... well... just not so much ^_^'