Since the raise of MMA, people have been focusing on its effectiveness on the street. There are basically two school of thoughts about whether MMA is indeed effective or not on the street. The MMA supporters think MMA is the closest to real life combat because of the rules and its usage of different styles of combat, therefore it should be the best style to practice if you want to get good at real fight. From the opposing side, it argues that MMA is just another form of sport and there is nowhere near to real life combat because the fight doesn't simulate real life situation where weapons, multiple attackers and guns can potentially involve. Hence, to train for real life combat, people ought to turn to Krav Maga or Wing Chun and Systema, that's the holy grail.
I am not here to argue which style is better on the street because it's pointless. But I want to guide you into looking at this from a different perspective. First, we need to define what a realistic combat means to you in the society you are living in.
Street fight is a very broad category and based on the level of violence, the reason of the conflict and the physical surrounding, there can be many scenarios. You can't generalize them. Therefore, we are only going to look at the kind of street fights we are likely to encounter based on the society we are living in. So if you were like me, living in a largely civilized society and a pretty good neighborhood, you are most likely not going to have to deal with street fights. If it does come to you, it will be most likely the fight against average person who aren't trained career criminals, like bar fights, parking fights. In these kind of situation, having trained in MMA, BJJ, Judo, Boxing or any form of full contact martial arts is more than enough to handle the fight, to protect yourself. Your body and mind are way tougher than average people outside of the dojo. You will be surprised to see how easy it is for you to handle someone untrained after spending some good amount of time at the gym. Now, if that average Joe is also trained in some forms of martial arts, then it really comes down to who gets there first and I have to say that having extensive MMA training is going to help a lot.
If you are talking about a different level of violence in extreme environments like prison, ghetto or combat zone where it is pretty much life or death situation, then things get really different. In this situation when you are dealing with someone who is trying to kill you by any means, martial art is an obsolete skill. You will need to use technology, modern tactics, mental warfare or even assassination in order to thrive in that kind of world.
I still advocate that in order to be successful at street fights, you need to train in full contact scenario. You need to know what its like to fight a struggling opponent, what's like to get hit, get thrown, get choked and get messed up before you build up the tolerance to physical confrontation and the toughness to get through the fight. If you are dealing with multiple attackers, weapons, ambush and so on, then what you really need to learn is not empty hand combat, you need to learn modern military tactics. And honestly, if you are always on guard about getting jumped by several people, you have problem fitting in modern society.