The quality of the women (based on intellect, personality, accomplishments, and appearance) who I've met in real life first before dating have been vastly superior to the women who I managed to find a date with through online dating.
Besides the restrictiveness of the online dating medium, specifically its inability to capture personality or warmth, I think another reason is because the women I meet in real life are able to evaluate me individually for who I am whereas in online dating you're practically always being compared to dozens of people.
I also think that people are overly picky in online dating and treat their specifications as sacrosanct instead of something to constantly self evaluate. For example, it's fairly common for people to specify a preference for a single race, usually their own. When I used to go on match.com I saw plenty of white women who explicitly noted they only wanted to date white men. Fair enough. And you know, a lot of white women I know in real life might have the same preference given the nature of growing up in small towns dominated by a single ethnicity and having consumed culture that largely glamorizes white men. But they also ended up marry Asian men, not through online dating but perhaps because they got to know them in college or at work or through friends. Likewise I'm certain that some of the women I dated in real life wouldn't have given me a chance in online dating. Perhaps it's because we could share laughter and gain trust in one another before even considering the concept of love. I'm sure there's also studies that show repeated exposure of a person has a positive effect on their perception.
And if you read the story in Aziz Ansari's Modern Romance, he mentions a similar anecdote where he met two Indian dudes, one who was struggling to meet anyone through online dating, and the other who exclusively just met women in real life and had no problems in that realm.
I guess my unscientific observation is that while online dating is certainly gaining in popularity and can be successful for some people, that it can sort of be misrepresentative of reality.