Well, both are sequels to light comedies that went well in the box office. I suppose he must be getting a good money for these jobs, that probably are far less demanding than actually having to build a new character for a serious dramatic role. Easy money, y'know? Let's not judge him too harshly, dubh-ban.
And actually I thought the mobster from "Analyze This" was a great character he created. Was it yet another gangster in his career? Yes. But we can't really say it was the same as the gangster in "Goodfellas" or stuff like that. A very funny construction IMO - not a superb performance, not an Oscar-winner - but hey, if he doesn't mind, why should we?
DeNiro may be just sick of "dense" roles, or just isn't finding any interesting ones. He's been there, he's done that, he's rich and not interested in accepting "dense" parts just to be "serious". If he doesn't like the dramatic parts he's offered, hey, those are some good humor roles he's working on.