Choose your own adventure
But why go through the guesswork? You could save a step by simply presenting the players with a few hooks to choose from, and then placing the characters on the map depending on which hook they choose. At worst, if they're not interested in any of the hooks you present, you're just back to the normal starting situation of the players offering ideas for what they're up to. At best, you and the players immediately share an understanding of what kind of game you're both interested in playing.
For that matter, you could even make this the very first step of starting a new campaign in any game - even before anyone begins to make up a character. That way you're also sure you won't get stuck with a bunch of characters (and by extension players) who have neither a connection to nor any interest in the scenario you were going to run.
A game like Talislanta seems particularly well-suited for this method - not only does the game come with a list of 48 different adventure seeds (already conveniently divided up amongst the various major regions of the continent), it's also got a wildly diverse set of countries and cultures to choose from if you need to go the improvisation route - just have the players pick a spot on the map, or pick an archetype's picture and say "I want to meet that guy". But this should work with most games, really.
I'm sure many GMs throughout the history of gaming have used the method of presenting adventure hooks to the players; it's not a new idea. The main points here are that it can be combined with the "put your character on the map" method; it lets the players tell you what they want to do, instead of dictating to them what they can do; and if you do it even before making characters, it helps you avoid the problem of inappropriate character choices.