How do you know when you have spent your money well for a video game?
My motto is "An hour for every dollar" at least in terms of quantity in a Video Game
However there are conditions. Take Professor Layton for example. I spend $35 for every game released in the series. But for only 1, I actually got more hours of gameplay, than I did spend money on the game. Why are these games, considered well bought? Because those Professor Layton games have excellent quality, in story, music and visuals. And that is where you estimate. How long you spent reminiscing how well that game was in quality, + how long you spent remembering and loving each part.
How do you measure whether how you made a bang for your buck or not?

if you can afford it and not feel guilty about the price afterwards . . . and, you know . . have fun.

An hour for every dollar? That's an awful expectation unless you play solely RPGs.

My baseline is simple, I'd expect 12 hours out of any $60 game depending on genre and things like multiplayer or sidequests. Divide that by price, and there you go. Portal was okay for $10 because it was exceptional despite being off by a half-hour. Games like 2D sidescrollers and First-Person Shooters I cut my expectations by 2-€ depending on the title.

And I don't want to play a crappy game for longer, so really that baseline is the ceiling. If it lasts longer hell yeah.

A movie costs $20 for 2 hours in Australia. A game is $80, so if I get 8 hours, I consider it reasonable.

It really depends on the game. You could find that your most favorite game costs $10, and you get 100 hours, because of replay value.

^ This sums it up for me.

You've never payed $60 for a game have you.

Thank god for student rates.

I don't. If I enjoy the game, money well spent. If I don't, money... wasted, I guess? I very rarely feel that I've wasted money on a game unless I really dislike it though, and that fortunately doesn't happen too often. Only game I can remember feeling like I'd wasted money on in recent times was Dead Island. I'm not gonna get into a debate about whether or not Dead Island was a good / enjoyable / better-in-coop or whatever game, I just personally hated it.

There's games I just don't get into - Fallout 3 and New Vegas spring to mind, but I don't feel like I've wasted cash on those. Just feel like I bought them and didn't click with them. It happens

Wait, "movie" as in going to the theatre, or "movie" as in buying it on dvd/blu-ray?

I consider it all as a loss as it serves only to provide me with transient entertainment that in the long run is entirely wasted. Regardless of how good the game is it is still just a waste of time and if all that can be said of my life at the end is "I was well entertained" then that'd be a sad end, indeed. Need to cut back on videogames, needless to say.