The Devil is a Part Timer got me out of my funk after the disaster that was the Naruto conclusion. That series is only one season, but it is hilarious. If you read the light the novels that continue the story, there's much more to be explored. I haven't been disappointed in what I've seen so far. Hopefully it gets a second season.
Here are some in my collection that make
Yu Yu Hakusho has far less emphasis on romance, although it is there.
I just discovered Buso Renkin, and while not as intricate a plot, it too had a very good, conclusive ending. Love the heroine in this one.
Rurrouni Kenshin seasons 1 and 2, then continue on with the manga. The third season is filler.
Full Metal Panic plus the light novels is great. One of my favorite endings ever.
Watched Accel World recently. It was alright. Only one season here too. I liked the fact that the hero is atypical in terms of physical appearance and the female lead is the strongest character. Not sure where the story goes moving forward in the light novels though.
Eureka Seven is very good if you stick it out to the end, though Renton gets on my nerves sometimes.
Last, but definitely not least... Stein's Gate. The development is awesome throughout. The movie that continues the story is even good. I don't remember the last time that a movie flowed so well with the rest of the anime.