These stamps are hilarious because they feature characters from comic strips.
In all seriousness, both Archie and Garfield have made substantial marks on popular culture and deserve whatever enshrinement they get. So congratulations to Jim Davis and all the folks who have been involved with the various Archie series over the years.
All that said, the Internet indicates that the last time the Post Office put out stamps with comic strips on them was 1995, in their Comic Strip Classics collection, which was limited to strips that debuted before 1950. Pogo, which debuted in 1941 and was therefore eligible, was for some reason nevertheless not included. And it has now been displaced by Garfield. Which, again, is not to say that Garfield doesn't deserve to be honored for its immense commercial success and all the fans it has brought to the comics section. But Pogo has a legitimate claim to being the greatest comic strip ever produced. Something's amiss here.
UPDATE: As Jaime Weinman notes in the comments, Calvin and Hobbes, Beetle Bailey and Dennis the Menace are all getting honored with commemorative stamps this year as well.* Still no Pogo, though.
Calvin is obviously very deserving, and though it might not be so obvious now, so is Dennis, both for its cultural impact and for Hank Ketcham's artwork. I concur with Jaime that Beetle Bailey is less deserving, though I don't really think it's any less deserving than Garfield is. Jim Davis has done more with various corporate tie-ins, but Mort Walker probably deserves some sort of recognition for all the popular comics he's created over the years and that, for better or worse, continue to fill up the comics section to this day. There are other comics, even other than Pogo, that I would have chosen in their place, but I can't necessarily complain about either of them receiving an honor.
It's probably also worth mentioning that Bill Mauldin is getting a stamp, too. Beetle Bailey doesn't hold up very well when compared to something like this.
*How I managed to spend half an hour scouring the Internet for prior instances of comic strip stamps without learning this information I have no idea.