Guys. Seriously. Do not turn a major monster race into comic relief. That's a decision for the individual DM to make, not for WotC to impose.
My take on goblins is that they're spiteful little bastards with an evil sense of humor. They're bullies, but not to one another--rather, they gang up to bully other creatures, using superior numbers and ingenious cruelty to cow foes who could easily squash an individual goblin. Their habit of riding wolves reflects this. The wolf is big and strong enough that it could rip its rider to shreds, but it's learned that such behavior results in swift, vicious punishment. Goblins love to stir up mischief and spread chaos.
Hobgoblins are goblins writ large, only better organized and with more focused goals. It's that focus, not physical size, that enables hobgoblins to dominate their smaller kin. The hobgoblins know what they want (conquest, usually) and keep their eyes on the ball, whereas goblins are easily distracted by the opportunity to wreak havoc.
As for kobolds, I don't use them much, but I like them as trapbuilders, tunnel-diggers, and engineers. Unlike goblins, they have no interest in cruelty for its own sake. They're cultish, with each kobold nest having its own strange religion that dictates its goals. (Dragon-worship is common but far from universal.) When kobolds attack human settlements, it's either for food or in pursuit of a religious calling. Otherwise, a kobold warren can often thrive quite close to a human town without anyone knowing it's there.