You're not the only one, it happened to me too since it was my first pokemon game, and I wanted to have ALL of them. I was like that a lot with DS games for some reason.

Pokemon Diamond - 782 hours

Kingdom Hearts 358/2 days - 342 hours

Fallout 3 - 563 hours

Fallout New Vegas - 395 hours

Fable 2 - 252 hours

I used to have nothing to do during those times.

As far as doing just story, Persona 4 Golden. Took me 90 hours just to beat story but im at 146 hours and counting trying to get a Platinum.

Seeing the numbers in this thread is one of the main reasons i avoid rpgs. They are serious time sink.

I think Mass Effect 2 - 34 (Did mostly everything)
Guild Wars 2 - Probably more but i kind of gave on that for now.

Do have Fallout 3, FF9 and Persona 3 in backlog. Haven't found motivation to get to them yet.

Oops, Hit submit on that one too soon

Baldurs Gate II w/ Throne of Bhaal -PC (200+ hours with mods and multiple characters, love interests, etc)

Lunar SSSC + Lunar EB (Played back to back) - PS1 (120 hours)

You are right, they can be a time sink, but if it is fun and enjoyable, who cares? Play through with multiple characters, different options, different story/ending. All fun.

The longest I played was Dragon quest 8. I think I spent about 160 hours in that game to beat the Dragovian Trials.

Xenoblade Chronicles with 180+ hours

Either Morrowind or Oblivion, both around 80 hours.

200+ hours on demon's souls

Final Fantasy XII and Dragon Quest VIII are the 2 RPGs that I invested the most time in. I clocked nearly 200 hours in each of them, for a single playthrough.