My best vote's gotta go to the... Like I dunno, the childishness of the games, the whimsical nature of everything! That is by no means an accusation of immaturity. I'd say there's more maturity in enjoying a game that makes you feel like a kid again than in constantly downplaying and deriding creativity and fun in favor of realism and grit, you know? It's got this... Well, really anything by Nintendo (it's Game Freak, I know, but whatever) has this certain instantly warm charm, and you gotta love that!
Worst part? I'd say the whimsical-ness has its drawbacks in the form of poor plot pacing. The simpleness of it is relaxing and unwinding, but still... It makes it very hard to, say, care about foiling Team Cool-Clothes or have any real sense of climax or shock for the reveal of the Champion's identity. Black & White nailed the antagonist angle with Team Plasma, I'm sure nobody would dispute that the story really benefitted from Plasma's constant threat and prominence. It distinguished them from, say, Team Aqua and Team Magma or, most disappointingly, Team Flare, who really only seemed to be majorly pressing for one comparatively small chunk of their respective games. As for Champions, I think Red & Blue's by now taken-for-granted twist of Blue being the Kanto League Champion made him the most personal and impactive final boss of the series, aside from maybe Red. Cynthia came close, but she wasn't really somebody that you just HAD to beat, like the smarmy cocky Rival of yours (it's sure hard describing him without breaking any profanity rules!). So I dunno.