And if you look at the early UFC matches grapplers virtually won everything ....it was only later that stand-up fighters started learning the guard position, and with just that one move they proceded to whoop the @$$e$ of grapplers.
In a real life situation going to the ground when you are facing 2 people means you will be trying to put a naked-choke on one ....but the other is standing behind you kicking your @$$. There is one story about two of the Gracie brothers (the best exponents of Brazilian jujitsu) who got into a street fight and got their butts handed to them. Going to the ground is nice if you are facing one person.
I myself was in some street fights back 'home' and in all of them but one i managed to take care of things standing up. And it was always against TKD folks so it was prety simple. The one exception was against this dude who managed to take me to the ground, but i knew some basic judo (i have concentrated on Jeetkunedo, kravmaga and did Shotokan ....but i have some basic knowledge of arnis and judo). That basic judo i had learned was enough to enable me to get into the guard position (he wasmuch stronger than i was and using brute force), wrap my legs around his neck, and basically choke him while lying on my back.
My personal thoughts is that the best thing to do is to know stand-up fighting (for real life), but at the same time know sufficient ground-work because there is a chance you may go to the ground.
Concentrating on just ground stuff (Braz. jujutsu, Japanese Jujitsu, Judo etc) can be a tad bit detrimental to your physical wellbeing if you face 2 people. However knowing them will enable you to take care of any ground situations (with my basic judo stuff i managed to basically toy with the dude even though he was by far stronger and heftier than i was ....and as i mentioned before i am not a paragon of the Mr. Universe contest). However knowing a couple of joint locks and chokes was sufficient.
As for the stand-up arts i would say Krav maga and jeet kune do are the best i personally have experienced. The only problem (as someone mentioned) is that the stuff taught can get you in legal trouble. Actually the reason i took some judo was because i knew if i went out with some friends and they started fighting i could not do anything with krav maga to stop the fight (pushing a pal's nasal bone into their cranium is not a good thing). As in Krav maga is good for a brawl ...but what if your drunk friend rushes your other drunk friend!
As for the traditional martial arts (TKD, Karate, gungfu) they are nice .....if you advance far enough and are mature enough to know that trying an ax kick on the street will get you hurt! Their problem is that they spend so much time on flowery stuff that looks nice in the Dojo (or Dojang) but on the street has zero efficacy!
Compare for example Muay Thai and Tae Kwon Do. Both are kicking styles known for great kick attacks ....but match a Muay Thai guy against a TKD person of the same skill and i can bet everytime the TKD guy will lose (and lose big). The thing is Muay Thai is by far more realistic than TKD, their kicks are meant to hurt (for what i mean compare a Muay Thai match ....which is full contact with teeth and blood flying around and most victories by knock-outs .....to a TKD contest which is basically point-sparring where the judges look for technical exponence). They are both kicking styles ....but in the street Muay Thai still retains its credibility.
Another example is Kyukoshin Karate (which is full contact and brutal) and most traditional styles of Karate (goju, shoto, etc) Your average Kyukoshin exponent is a guy who can wreak damage in the ring and in the streets! Someone who has been taking Kyukoshin for just one year, and taking it regularly and diligently, can beat the heck out of many people. In traditional systems you have t take them for a long time to get really skilled. True, after a year you can do nice kicks and pack power .....but you also spend a lot of time doing katas and all that stuff.
When i left shotokan i had a ni-dan (2nd degree black belt) after spending years in the art (i started in 3 grade and stopped when i was 19). However when i started jeet kune do (around 18) in a year i had learnt more street stuff than all those years in Shoto! And in Krav Maga it was the same.
And do not get me wrong ....Shoto and TKD is not nonsense. I know some Shoto people i would not dare mess with .....those guys are monsters (Shotokan karate is a 'hard' style of Karate that uses a lot of power in the strikes, and those guys are huge behemoths). However those guys are all 3rd degrees or higher (and from outside the US .....hence they did not start getting black belts in grade school as is apparently common here) I know i am fast, and that is one of my greatest strengths since i need the speed, but tangling with those guys and getting a single punch would probably mess me up considerably! However getting into a fight with 3rd degree Gojuryu or 4th degree ITF TKD folks is virtually impossible. By the way it is in such levels they start learning the real martial art ....in that 1st degree black is when you start learning the 'real' karate and its self-defense applications (and that is why i would not tangle with the 3rd degree folks from back home). However here i ahve met kids who are black belts and cannot even keep the local bully from stealing their lunch money .....and i wonder! Is their sifu/soke/teacher etc really legit? How do you give someone who has not even started middle school a black belt and have a clear conscience?
Anyways a 2 year student in Krav Maga would probaly beat a 6 year pure TKD fellow