Effectiveness is contextual. As an avid BJJ-er from the early days of it hitting U.S. shores, as well as a lifetime stand-up martial artist who, in his younger, dumber days, went out of his way to participate in confrontations to see what worked...
I have been in both scenarios...using BJJ in the street, choking a guy out while his friends booted me in the head, calling for a change in strategy (variations on this happening 2-3 times, total). HOWEVER...I have MORE OFTEN gone to the ground, in the streets, quite successfully, on asphalt, cement, wood floors, carpeted rooms...and choked the living snot out of some cheeselog who more than had it coming! (I discovered early on that if I could not justify force prior to engaging, I couldn't remember anything I studied once in the fracas).
I keep reading woulda-coulda-shoulda posts about the liabilities of BJJ in self-defense...that it is sportive only...developed in the context of rules, and therefore inherently deficient...etc. What, you think BJJ guys throughout Brazil...a country with an alarmingly high violent crime incidence...managed to get through the last 75 years without ever having to fight for their skins? You think Olympic Judo players couldn't drop you on your head so hard, that future aggression ceases to be an option?
"They were feuds"...what context do you suppose most Asian martial arts were developed in? Battlefield tactics? Hardly...too many unlikely impracticalities buried in form to have come from "tried, tested, and true" arts straight out of border skirmishes or invasion campaigns. The guys who were really good were put at the front of the lines, where odds alone eventually removed them, and their knowledge, from the face of the earth. We get handed down the tips from the guys in the back who either ran, or were lucky enough only to have to finish off the few survivors from the opposite side.
"What if there is more than one guy"...been there, done that, and if you truly ever face more than 1-2 guys, use your head and your feet for getting the heck out of there, and not bunting and kicking. Don't be silly enough to assume that people in multiple opponent situations attack one at a time, on cue, like they do in Bruce Lee movies. Certainly, don't be silly enough to believe that your kung-fu is better than their kung-fu, to the tune of emerging victorious from a 5-on-1 knock-down/drag-out brawl. On the ground or on your feet, if there are enough guys, you will go down (learn to use your arms to cover your temples while tucking your chin hard to protect the throat...everything else is expendable, and can be surgically corrected if a bystander calls 911 in time).
"What if the guy has a knife"...contrary to popular belief, some schools train for this possibility...quite well. And when all is said and done, it is wiser to run from the knife and charge the gun, anyways. (try stabbing a guy who is running full-tilt in the opposite direction...kinda hard, no? Now, sight the runner down the barrel, and squeeze off a couple-a rounds...easier, no?) I have fought for my life against opponents armed with knives...it is pure chaos; all the technique training in the world will only barely prepare you for the mayhem that fills the air when a decent knife player pulls on you. Typically, count on getting cut (you will shed more blood than he); having accepted that...if running is not an option...try to control for the location of the cuts (distal appendages more than proximal; dorsal surfaces of the forearms more than anterior; opposite for the lower extremities). And, despite your preparations, the outcome will ultimately depend more on luck, then skill. That being said, it does seem true that chance favors the prepared mind. Still, run. Your karate/kung-fu/kickboxing will serve you little better than somebody elses BJJ. Matter of fact, since BJJ guys spend more hours working on controlling appendages in tight quarters, I would be more likely to put money on the Gracie who takes the knife fighter to the ground, then the standard TKD or Kenpo guys who try to execute some one-steps or self-defense techniques...things get blend-o-matic ugly, fast. If you're lucky, you won't even know he had a knife until it's over...adrenaline can mask a lot of pain and narrow a lot of perception.
Gi...no gi...I've choked out people in ski jackets, pretty ties, and tank tops...it's all good.
Big / Not Big...I've posted on this before, but in a nutshell: In the vein of "I've been rich and I've been poor...rich is better"...I've been small and I've been big...Big is better. Choking people out is easier with 22-inch guns and a chest then it is with 15 inch arms, and a sunken hole where a chest should be. That having been said...I've had my hind quarters kicked by little guys on the mat. As a bouncer, though, it was never the big guys I worried about: They were easy, as they would predictably try to use their size and strength against me, and somehow magically manage to conveniently place themselves in my traps. The small guys were unknown quantities: fought harder, came back for more-more often, and were more likely to have some dirty trick up their sleeve you had to watch out for (i.e., one guy always made sure he had one drink in his hands, and an empty glass or bottle in the other...drink to the eyes, followed immediately by a glass to the head...all while aiming a kick to the groin).
BJJ works in the streets, quite well. Granted, I coulda been killed the few times I went to the floor and there was more than one guy. But I also coulda been killed any of the dozens of times I was standing up, and there was more than one guy.
As for elevation? Guys like Rickson are a specimen, and would (and do) excel at anything they do. The art may have channeled the genetic propensity to be damned good at anything, but the man himself is a dynamo at anything he's ever attempted...surfing, volleyball, name it. I hated these guys in High School: He could have never seen a pool table in his life, but after watching for an hour to learn the rules, he'll be taking your money by the end of the night.
No, the arts aren't elevated by the phenom's who excel naturally, but by the guys who have to try harder, because they don't have the talent of the others. Funakoshi, Ueshiba, Carlos and Helio all started off as small, weak guys who had to rise to an occasion in order to acquire the top of the mountain. THEY propel the arts, NOT the guys BORN on the mountain.
Salud!
Dave