If a fight does take you to the ground then obviously martial arts such as jujitsu and judo will come out top but the danger is once you're on the ground your attacker could easily pull a knife, or his friends turn up and, instead of being on your feet where you could have a chance at running, you're on the ground.
Defending against strikes isn't overrated, often it's the first move made in a fight and if you can't dodge, block or counter it efficiently you could be in big trouble.
I did judo for a while and while it was fun I definitely think it would need to be accompanied by another martial art that covers striking to be used as self defense.
But yes, the absolute best option is run if you can lol