+2
There's far less risk with a sequel, or a reboot/remake, because of the brand recognition, so they're worth spending the money to produce. As to what makes a sequel "good," that's determined before you ever saw it: Did the production meet or exceed its goals with this project? If it's a comedy, is it fresh? Is it funny? Then, yeah, it's a good sequel, a good comedy ... a good movie. There's so much marketing that goes into Hollywood movies now, more than ever. They don't want to take chances, they want a sure thing. But whether all of that green-lighting, promotion and brand-recognition pays off is still up to the audience.
What I love about Hollywood is that even now, there are still surprising pictures, when all of these crap movies are being pushed on us, where it's fresh, original and ultimately influential. But movies like that are not the norm, because people don't have the money to go see everything. Given the choice between a movie they've never heard of, or another movie about characters they already love, they're probably going to go with what they know. It's not a guarantee, but it's a very safe bet. Besides which, the studios already own the rights to past titles and franchises, that people still remember, or heard about, so it doesn't make a lot of sense to just sit on those, to preserve the purity of what was released previously. And part of that is nostalgia, which also involves passing that onto their children. So, sequels are a good idea, they can go on for decades, even ... same cast and everything and remain profitable.