Sure, we could blow smoke and tell you that the best trained actors are also the most successful, but acting is not the same thing as lying. The truth is, you can have your BFA/MFA/Union Card/rock-hard abs, and still never book a role, while some fresh-off-the-boat Ohioan can be here three weeks and get the lead in the next Michael Bay travesty—no offense, Ohio.
Does that mean you shouldn't get training? Not at all. Sure, some people get rich and famous because their uncle knows the assistant director on the Jaws remake, but most of the actors you've actually heard of have gotten at least some training.
Some go the college or conservatory route, while others take random class after random class while auditioning and holding three jobs. The method behind your madness is not the important part, it's that you're improving and refining your madness until it turns into artistic talent.
Sure, we hear you say, that's all good, but some fabulously successful actors have made it without anything more than a high school education (some even less). That's true, but the more time you spend perfecting your skills the better your odds of setting yourself apart from the other riffraff and breaking through the haze of mediocrity.
You also never know when you're going to audition for someone who went to your school. A connection like that can be all it takes to catapult you to a steady paycheck—for a few months, anyway.
And, although it definitely helps, you don't need to be great looking. Of course, you'll mostly be relegated to second-fiddle parts made to fit your particular oeuvre (or in actor speak, character roles). Not everyone is going to get to play the lead. But hey, even Jeff Goldblum can be considered a sex symbol. It can't be that hard.