The longest game I played was oblivion. I have to think about the hardest.

Longest? Baldur's Gate (From the beginning...through Throne of Bhaal. BLows Oblivion out of the water)
Hardest? Teenage Mutant Ninja Turtles

Dragon's Lair for the NES, though I can only guess about the length.

For how long it took me to get to the third screen (note I didn't get past that screen) I can only guess the game is eleventy billion hours and would make you lose all your hair and several windows.

Impossible Mission is a rough road -- I was immediately reminded how easy games are now when I bought the new one for DS.

 I've been playing Morrowind off and on (less so in the last two years) -- same character -- since 2003.

Ultima 7 The Black Gate

Hardest game I played was original zelda, Longest game I played was animal crossing, It just doesn't want to be finished

the longest game ive played is GTA:triple pack and the hardest i cant really think of

Hardest : Ninja Gaiden Sigma ( go go 714 death beating the game in normal on my first time, of course now I clear normal in 6h with 0-1 deaths but still).

 Longest : Morrowind or FF X.

I found the hardest game but never played ithttp://www.youtube.com/watch?v=hIXRgppi04M . Idk know what the language is or what it says.

hardest good game, probably the nes ninja gaiden
bad games seem to get stupid hard, the previously mentioned nes dragon's lair is insanely hard, you actually have to walk in sync with moving platforms or you'll fall off, and if one pixel of dirk's foot past the edge of a surface he'll die, as he can't jump or turn around with out falling,
longest, probably the complete shining force 3, each scenario is around 35 hours so around 105 hours to complete the entire game