I don't want to end a campaign thinking, "that's it?" I also don't want to end a game thinking, "finally!" The game should be long enough for me to explore the mechanics fully, yet end on a high point before the fun turns into a grind.

As a gross generalization, around 15 hours before multiplayer is the sweet spot. Shorter & sweeter is fine, as well as longer & more complex, but 15 hours seems like a decent rule of thumb.

bloodborne is prime example how a game has to be 20-50h campaign. +real more content with chalice dungeons. MGS5 is also an example how to have many content for your 60$ game with the Singleplayer, multiplayer + the FOB system

It depends on the genre. From RPGs I am expecting around 100 hours and from other genres 15-20 hours.

The jig is up!

I like to compare this another form of entertainment: Movies.

If movies tickets cost approx $15 ticket and gives me around 2hrs of movie length, then $60 should give me 8hrs. So with that said, I expect a $60 game to give me at least 8hrs of length in gameplay.

...but then there are games that just above and beyond giving you the best bang for your buck like CoD BO series.  Great campaign, great mp, great zombie mode giving gamers hundreds of hours of non-stop fun, and best of all there's local co-op so you can enjoy it all with a friend.  People can say what they want about CoD games, but Treyarch knows how to make a dam fine game.

It entirely depends on what the game is. There is no one size fits all.

Over 20 hours. This is why Fallout 4 is the first game that i don't mind paying full retail for, since The Witcher 3.

Don't care. I buy games that I want to play, not waste time with.

I second this!

I don't care at all. Superb 20min. experience is better than 20h of mediocrity.