Depends how you define great.
I'm slim but not ripped; I'm no fitness model nor do I have bulging muscles.
I've only been seriously weight lifting about 6 months (prior to that just regularly participating in sport). I have changed my diet to match the training (although I'm not taking any supplements) and I've noticed some changes so I'm moving in the right direction. Whether I will look "great" is another matter - but I am pleased with how I look now and think I will look even better in 6 months' time!