Hm! Having experienced D/P and acquired a standard team, I have added a few more favorites. With the release of the complete Gen IV list, I was skeptical, mostly because ugrades and legendaries took up much more of the list than they did in past generations. Despite this, the new Pokemon are fairly impressive, both aesthetically and capability-wise.
Roselia was a Pokemon I didn't particularly like in Gen 3. It was just strange to see a single stage grass type that didn't particularly stand out (and then I met Tropius) and was presumably EV fodder, but with Gen IV, I began to see it in a new light, having a 3rd stage sparked my interest and I trained one. Turns out all these pretty perfect-for-contest moves do a fair amount of damage (meh, my swellow used to wipe out roselias before they could even touch their magical leaves) and I'm hoping my Roserade, in all its elegance and Sentai-ness, will play a key role in my E4 victory. (Bertha sweeper ftw.)
Next came Buizel. Up until Dawn caught one, I didn't see anything particularly interesting about them, and its evolution wasn't very pleasing to the eyes. But Dawn's Buizel was so badass. Of course I could only dream that the game would have a Buizel with a perpetual scowl that crossed its arms, but meh. Turns out Buizel is essentially a water-type Pikachu, and makes a fine sweeper. Besides, in my second playthrough, I captured another Buizel, to my surprise, it had the same Lonely Nature, same level and exact same stats. Who can argue with a ridiculous amount of coincidences like that? xD
The rest I favorited simply because they made excellent team standards. Luxray was pretty much a Lion-esque Ampharos, one of the reasons I adore GSC so much. Murkrow, though I have never trained one back in Gen 2, was an unexpectedly awesome Flying sweeper, sharing the same weaknesses to the early birds but rather than an immunity to ghost, is immune to the deadly and confusing Psychic attacks. Infernape, being the only other fire type in the game and possesses the decent stats Starters are known for.
If I ever do finish the game, I'll try out Toxicroak and Lucario, seeing as these two have such awesome artwork from Ken Sugimori ;D