I think that kpop takes from a lot of genres if you start looking into it more, but you're more or less right. The most popular kpop songs are almost always bubblegum/electronic/dance. I wouldn't classify Gangnam Style as bubblegum pop though, and the interest isn't as much in the music as it is the juxtaposition of a chubby Korean man dancing his *** off to synth-y eurodance music.
Bubblegum pop lends itself very much towards the idol-centric business model where the music's main goal is actually to reinforce the idol image rather than, well, be music. This is a pretty common element with SM Entertainment artists up until the mid-late 2000's. It's a strong reinforcement of the whole 'look how cute/innocent/lively/etc I am' theme that kpop idols are known for. They seem to be weaning off of it lately though.
The runner-up genre to these would probably be the ballad/r&b type stuff, which is cool.