Personally, I hate (HATE) baby pokemon.... I think they are useless.
Anyway, the only ones that should evolve are the ones that are crap right now, but that could at least be usable if they had better base stats or type/moves combo... And there are many of those out there. After doing the list of those I wanted, I noticed most were from Gen II.... Odd.
= It looks cool, but the stats/types/abilities simply kill this pokemon as soon as it comes out of its pokeball... Can be 8x weak against fire! Nice.
= At least other pure-poison types like Weezing and Muk serve a purpose.... Arbok is only nice for his Intimidate.
= They could have gone further in the spider type. How about a hairy/scary tarentula? Or a jumping black widow?
= Good concept, but hardly usable with those low stats...
= Again, the concept was nice, but it's useless with current stats.
= Ugh... That one is fail. Probably the worst fully evolved pokemon in existance... It just screams for better stats.
= Nice type combo, stats just average enough to be decent, but still could be much better. And make it as big as a real giraffe!!
= The octopus is very cool, and it has decent stats, but the concept could have been pushed so much further! Make it bigger and badder! (as in make it so it doesn't look that dumb...)
= Waaaaay too average... He looks nice though, and makes an AWESOME HM Slave!
= The firefly concept had very good potential, but they stopped there. It could evolve in the first ever Bug/Fire type!
= Make it like a real panda!! With actual stats to warrant its existance.....
And I won't even bother with Gen IV... In my opinion, most of the ones with crappy stats are Pokedex fillers...