I would go so far as to say he did make a great game, Populous was one of the best games I've ever played, it really was the game that made me fall in love with video games in general (not the first I played, but possibly the coolest). EDIT (Add): didn't know he made Syndicate, ever since I played that game that's what I secretly want ALL games to be, that game made me fall in love with the cyberpunk genre. You made two great games, they didn't follow any lame mold, they were totally unique, fun as hell, easy to play, difficult to master...they were GREAT games. Do something like that if you want a great game.
Beyond this, if Molyneux is aiming for the 5 mil sale mark to declare a great game, sadly I don't think he'll ever make another one. There are great games that sell, ones that don't, terrible games that sell great, and anything in between, but I am firmly convinced that any great game that came about wasn't trying to make a game that'll sell x copies (not to be naive I'm sure they all hoped it'd sell x^100 copies), greatness, in anything, typically isn't mass-marketable, otherwise it wouldn't stand out enough to be great.
Beyond this, if Molyneux is aiming for the 5 mil sale mark to declare a great game, sadly I don't think he'll ever make another one. There are great games that sell, ones that don't, terrible games that sell great, and anything in between, but I am firmly convinced that any great game that came about wasn't trying to make a game that'll sell x copies (not to be naive I'm sure they all hoped it'd sell x^100 copies), greatness, in anything, typically isn't mass-marketable, otherwise it wouldn't stand out enough to be great.