It's easy to look back at something that failed and say, "Well, if only they'd done this or that instead, it'd be great..." and go about your day. It doesn't change what's happened, but we like to feel smug for adding our two pence's worth.
The same goes with video games, too. You could be looking forward to something for so long, that when it comes out it doesn't meet yours or the masses' expectations. It could be that there's just one thing missing from it, that could have made it oh so much better.
It could be something as simple as not spoiling the exclusivity of an upcoming game on one console. Perhaps even not making us pay for single player, or worse, removing it completely.
Conversely, it might be just that little tweak to make a game's multiplayer online that would shift units tenfold, as your friends would be able to assist from afar.
Now, whilst some games on this list have gone on to shift millions, they haven't done it overnight. Nor are these flops, it's just that these little nudges (and the benefit of hindsight) could have really helped them reach their potential earlier.
So let's have a look at some games that I bet developers are kicking themselves for not thinking of tweaking sooner.