A lot of interesting animes being discussed here, a lot of these I haven't even seen. Thanks for the overviews too. They're very helpful.
Doesn't sound great when you say it like that, just because they're long series doesn't mean they're bad nor time-wasting. Especially One Piece. If it wasn't a great series it probably wouldn't have lasted as long as it has.
Naruto is an enjoyable series for me overall, but what annoyed me most was the fillers, too many and too frequently. Season 10 felt like a filler marathon for me. Naruto usually excels when it comes to the fights, animation is good and the music suits it well, the fights also consist of strategy and teamwork which always keep me entertained.
When it comes to the Anime I liked Part 1 better than Part 2 (Shippuden) mainly due to the extremely slow pace of Shippuden, I used to watch the dub years ago on Jetix but when it was cancelled I re-watched the series with english subtitles and I enjoyed it just as much (apart from the odd lack of emotion at times).
For Naruto I would recommend both. The Manga's pacing is much better and there are no fillers. Whereas the Anime does have the added comedy and a very good musical score.