There really is a scarcity of Regular Show material. I've seen Adventure Time stuff at Kohl's and other fairly big-name department stores, but to get my Mordecai and Rigby shirt I had to go to a Hot Topic, which isn't exactly the kind of store that welcomes people with open arms. I'm waiting for the "Mordecai and the Rigbys" t-shirt to come out.
I want a High Five Ghost plush. I could probably make one, but I'm not that handy with that sort of thing. Hopefully in time, we'll see more stuff... maybe an actuion figure line... though I'd tend to think one of those overpriced blind box ginzu toys from Kid Robot would be more likely.
I haven't even really seen any new CN show since they dug themselves into a grave in 2004, but even before then, I didn't like the way they suddenly treated every new show of theirs like a cash-cow... Dexter and Powerpuffs had a little bit of merchandising, but that was because they were genuinely two of CN's more successful and popular shows... EEnE EVENTUALLY got more merchadising when they realized it was a hit as well... but once KND came out (which I quickly got sick of because of how over-rated it became), it seems like every new show CN added to the network instantly got merchandising galore.
CN really lost it with the horrid line up of the disappointing, but watchable Camp Lazlo (Joe Murray should have brought some Rocko writers along with him... that is, if half of them didn't move onto other things), Squirrel Boy (which I never have seen, but I am a fan of Everett Peck's artwork... I doubt it would be funny as Duckman if Lazlo was any indication), and, worst of them all, My Gym partner is a Monkey. That was just non-stop Monkey Butt humor.
Sure, I'd like to say CN's glory days were back during the Dexter/Cow and Chicken/Johnny Bravo/Powerpuff Girls, but even then they had some hit or miss (mostly hit) up until they canceled Fosters and Grim. What ticked me off was they pegged Chowder and Flapjack as shows that would save the network, and they just couldn't wait to cancel them for shows about 5 year old internet videos and 5 year old stolen programing from Discovery Kids.
Again, this was because Hanna Montana was popular at the time, and every network felt they needed to clone their programming to compete. Nickelodeon's still in that phase.
Still, Regular Show and Adventure Time are matter of taste things... took me more episodes of Adventure Time for me to get into than Regular Show (which pretty much won me over with the Hummus Rap, which was the first one I saw). But that stuff, as well as the DC action shows, put CN back where it needs to be... they have a ways to go, IMO... but they're more together than Nick is. They refuse to give any new Nicktoon a chance, and frankly... Spongebob wasn't popular or even mass merchandised until maybe the second year it was on. I'm guessing no one remembers the show premiered in 1999! If Spongebob premiered today, it would last a half a season and get replaced with another Big Time Rush ripoff. That's why I'm VERY worried about their TMNT series. At least we're getting a great IDW comic series from it.