I adore the Bug Catching Contest in HG/SS. Although bug Pokemon have honestly been a type, I don't favour in general, every time it was on, I'd leap at the chance. The prizes were great in my opinion, stones are definitely a good reward. The Bug Catching Contest also has loads of benefits - You can catch Pokemon like Scyther early instead of waiting for so long.
I'll have to be honest here, usually I come second in the Bug Contest. I rarely come first, maybe Catching Contests aren't really my thing. I dearly wish they were held everyday, that would be awesome xD!