Its generally that way with most TV series. The only televised anime I've ever watched is "Digimon" and "Pokemon". I was quite fond of "Digimon", but backlash against "Pokemon" is basically the reason I was so reluctant about taking anime seriously. As for anime movies, I've watched "Spirited Away", "Castle in the Sky", and "Princess Mononoke", though I'd also like to watch Miyazaki's other big-name movies. ("Kiki's Delivery Service", "Howl's Moving Castle", and "Ponyo")
With that said there are some shows that I wish would be hour-long. I haven't seen enough anime to know whether it applies here, but judging by how well "The Clone Wars" is handling three+ episode arcs, I would love to see how effective they can be with an hour. Been watching an animated series about Batman on Boomerang ("THE Batman" apparently, not the one I saw when I was young I think) and it seems like the time is what causes it to fall into a monster-of-the-week pattern.
Of course, according to stereotypes, anime probably wouldn't be serious enough to last longer than thirty minutes on television. I'm sure that's just based on the likes of Pokemon though, so I'd love to hear otherwise.