So, many people here have made the point that being on the ground is not the place you want to be in a self defense situation. I agree. But, I think we might be forgetting that sometimes, its not your choice to be on the ground. There are people out there, that can take you down and pin you... and there is nothing you can do to stop them. We even see examples of this in MMA. Some guy comes in, who is a really good striker, with an amazing take down defense. Eventually, he fights someone who can take him down... and all the film study and fight prep for that one guy, doesn't stop the take down. Now what? While being on the ground may not be your ideal place to be in a situation... the choice may be made for you, whether you agree with it or not.
What BJJ brings, is a lot of great sweeps, escapes, reversals and even submissions. They also work from more positions than just guard. In my opinion, if you think that in a certain situation, the ground is the last place you want to be... that makes a better argument for studying BJJ, to learn to sweep and / or escape while on the ground, to regain your feet. (before or after choking the guy out...
) Judo and Sambo would be good too... but for regaining your feet, I think BJJ is the king, as thats exactly what they focus on, the groundwork. If punching a guy off you, when you are on bottom worked that easily, why don't we see that happening more in MMA? I have seen a guy KOed from punches by the guy on the bottom... once. I have seen an awful lot more guys on the bottom take a serious beating because they had no real experience there.