For $60? 40 amazing hours

I typically only buy a game if I know I will be getting at least one hour for every dollar I spend, which is why I typically don't buy games at full price, unless I'll most likely be playing the game for a long time, such as Smash Bros or Pokemon. So, my ideal length for a $60 game is at least 60 hours, otherwise if I won't be playing that long, I'll just wait until it gets cheaper.

It depends on the type of game. For more linear types of games, I like 10-15 hours. Open world type games like Zelda or Assassin's Creed or Far Cry, 20-25 hours is good.

There is no perfect length. While I'd be okay with 5-10 hours for a cineastic game, that would be inexcusable for an RPG. For those, I'd like to have 40 hours for the main story and additional 20 hours if I feel like I want to spend more time in that world.

I thought it was pretty fun, though it can get repetitive as most games do. The main problem is once you get the best weapons you'll find you're essentially invincible and there's nothing really to do, but you should have enough fun before that. 

Depends on the type of game.

Zelda 3D: 40-60hours
Metroid: 12-15 hours (even Other M or Super Metroid are around 5-6 hours)
etc.

Vanquish is not criminally short. It's just short.
It packs more action (quality by the way) in its short time, than all the other TPS/A. It's more fun than them as well as single player.

It depends on the type of game.

For example, Resident Evil 6. Its a very long game that reuses levels and spans multiple sides of what is actually a short game. It would have benefitted from focus and a shorter campaign.

A game like Skyrim, is supposed to be an engrossing RPG, so i'm expecting alot of content as the games have systems that lend themselves to a high level of progression, exploration and customization.

A spectacle shooter like Uncharted, cant afford to linger too long. I would say less than 10 hours because repetition settles in quickly after killing wave upon wave of enemies. The only thing that changes is the background.

An action sandbox like GTA or AC has a ton of boring and repetative collect a tons wich increase the length but also the boredom of the games.

So, i would say, that ideal length depends on quality of the game. Developers shouldnt be afraid to make short but high quality games, because not only are they enjoyable, but leave the customer wanting for more.

But of course, this has to be taken with care because publishers will just distort that into:" lets launch incomplete games for full price", and that isnt ok at all. It should still feel like a complete experience, and it should lead into the next title. The only problem i see with the Order is that they said they arent making a sequal and that it ends on a cliffhanger. I would have to be insane to jump into it only to be disappointed even if i enjoy it.

20 hours is a nice length in general. Maybe 30-40 for RPGs though.

depends what kinda game it is but at a minimum i want 12-15hr for the campaign and a total 20-30hrs to 100% and some kind of competitive multiplayer

if its just a 12hr campaign or less with no MP like we see with until dawn and the order then the game should be 40 bucks or less

there are other games like gta where things get tricky theres alot of content and a MP but alot has been striped with gta4 and 5 compared to the ps2 games