I can't really come up with an overrated and at the same time interesting anime. Personally, I like Dragon Ball Z; I know that there is no long plot with unexpected turnouts or with a thoughtful and intricate development, but the fights have somehow a vertiginous rhythm that catches your attention immediately and make you feel like willing to be part of that fight (who didn't imagine himself being in the air and hitting that way they do in the back that particularly annoying guy, throwing him roughly to the floor
).
The characters have pretty much charisma and they are very expressive as well; the arrogant faces they are sometimes drawn with is just amazing (mostly after raising a new Super Saiajin state). That feeling of "now I am really powerful, you will be wish you were not born". Dragon Ball Z caught not only a big audience among those ones who didn't know what Anime is, but it has been also seen by a lot of people who were inside Anime already.
Sometimes the critics it receive are not deserved; the problem is that nowadays it's a common way for some people to feel themselves intelligents and original when criticizing something bellowing to the "mainstream". I'm not pointing at no one, there is also very often people with valid critics to it.
Sorry if I went way too much out of topic
, sometimes it's normal in me unfortunately. Back on it, even though I like Dragon Ball Z, I believe Dragon Ball GT to be overrated. It's just some Dragon Ball and Dragon Ball Z reprise in Universal scale, some characters (Piccoro Daimaku -which I believe to be his complete name, not sure though-, but mainly Vegeta) lost their violence -a significant characteristic they had in Dragon Ball Z-, fightings lost violence as well, and it got boring. But it's popular just because it is Dragon Ball (Toriyama, we missed you
). I would save only the last 2 chapters from there, for having the single plus that the fight is a little bit "Dragon Ball Z" like animated, and that it is the closing of the whole cycle.
About an underrated Anime, I believe I pick Gasaraki. It belongs to a "historical period" with a good amount of excellent Anime (Evangelion, Escaflowne, Cowboy Bebop, Lain). It has an interesting plot, mixing japanese traditions and mythology with nowadays society and technology; a very good opening and ending (both song and animation); animation, character design, mecha design, all of them are really good. But since it is a little bit dense, and since it's not full of those spectacular scenes made in order to easily catch audience, it's practically unknown by some people. That's my opinion at least, and I know that I'm risking myself to receive as an answer "it is a boring anime" (shrugs).
Here is a list (all based off current outlook).
