Lately I've been reading a lot of articles complaining that games (especially RPGs) are too long and blaming that for many gamers not completing the games they buy. One article on IGN Insider even proclaimed that less than 50% of gamers finished the ridiculously short Ultimate Spider-Man according to a survey by developer Treyarch. That got me thinking. I almost didn't finish USM, but it wasn't because the game was too long, it just didn't feel balanced. Not that it was a bad game, but the story was too short, and the game play within the story mode throughout the entirety of the story mode was chase bad guy down, beat bad guy up. Treyarch had apparently hoped that the side missions would break up the monotony of the story line, but it didn't. Many gamers, myself included, that I know did the minimum required side missions to get to the next story segment, only to have to chase down a villain, and then beat the snot out of him. The chases got way too old way too quickly, and chasing villains down with Venom was not fun at all, it was a painful experience. Worse yet this game was supposed to tie into the comic book, and when Silver Sable was introduced in the comics Peter Parker had no idea who she was, so I feel kind of gypped. Had the story been longer, deeper, more organized, actually a part of the comic's continuity and not filmed so weird then getting the story itself would have been a lot better, and had the primary missions of the game not been so repetitive then I'm sure a lot of gamers would have finished this title. I don't think its length has anything to do with it.
As far as I'm concerned the three games that have been the best financial investment I have ever made have been Final Fantasy XI, Sims 2, and Guild wars. Why? Aren't I the type to play for story? Yes, I am, but when the story is over I admit that the game collects dust. From a purely game play standpoint those three have gone above and beyond as they never really end, and all feature such a massive amount of different things to do that getting bored with the titles are nearly impossible. These games feel balanced, USM didn't. I think the more game there is the better of an investment it is for me. I hate spending $50 only to get 5 hours out of the game.
RE4 had a perfect length, 20-25 hours, and more than enough story to flesh out the game play. Metroid Prime 2, however, ran out of story 15 hours before I beat it. See how balance is important?
Games don't need to be shorter. Shortening the games will reduce their over all value. They need a wide variety of fun things to do, and a deep story to keep people's interested, as well as great game play that isn't too hard (DOA4 Shame on you!) and won't cause people to break stuff because no matter how hard they try they just can't beat (That blasted Kasumi clone at the end of DOA 4). Balance is an absolute must.
While a number of editors can complain about games being too long I don't know anyone who complained that RE4 was too long. The only complaint I ever heard about RE4 was that it ended. Same for Jade Empire, nearly universally criticized as too short, especially with such awesome game play there, I shed a tear when I realized I had beaten the epic and Jade Empire 2 is probably the next gen title I'm looking the most forward to at the moment.
Only one Zelda game has ever had complaints about length and that was the Wind waker, where people didn't gripe about the over all length of the title itself, but the travel time involved in going from island to island.
No one ever complained about the length of Metroid Prime either.
To summarize, game length isn't the reason people shelve games before finishing them. A failure to have a reasonable balance between story and game play and difficulty are. If a game gets too hard, it gets shelved (DOA4 sans the online mode cause that's fun). People don't have fun having their butts handed to them every time without fail (Stupid Kasumi clone). People get bored is the main game mode is the same two tasks over and over (U Spider-Man, Chase bad guy down, beat him up), and people loose interest if the story elements fall short of the game play length (Metroid Prime 2's story elements were far too sparse to keep up with the 35 hours it took me to get through it, but then again that might have been cut down by about 15 hours had Nintendo not done the whole losing life to the dark world atmosphere and having to find safe spots to recharge your health.)
My recommendation to developers is to just make sure everything is balanced, a good story combined with innovative game play, and reasonable difficulty that is challenging but not overbearing and people will buy the game and complete them.