Something that people should very much keep in mind here when it comes to Counting Ticket Sales to determine the success of a movie...
1 - How many of US have watched Gone with the Wind, own it on DVD, much less Blu-Ray?
2 - Compared to 20, 30, 50 years ago, the number of theaters screens available. Go back to the 70s, most theaters had 2~4 screens. There is a lot more competition with 32 screens.
3 - Many people have HD-TV with large 50+" screens and amazing sound systems. With Blu-Ray and such, this means a person can watch the movie once (if at all) in the theater and then buy the Disc media and watch it many many times. Back when "Gone with the Wind" was made (a chick flick), there was NO DVD, VHS or other means to watch the movies at home. Not until TVs in the 50s started coming out.
Even when Star Wars came out in 77, the theater was the ONLY way to see it for a year or so. And a VHS / Laser Disc copy was about $100! A plain mono-VCR was about $1000 in 1980, only hitting $400 in 1985. (People bitching about Blu-Ray players & PCs costing $400~600 is kind of funny... with inflation, my 1985 VCR would be $800 today).
So yes, Avatar is a very successful. Its still doing very well in theaters and will do extremely well with blu-ray and 3D blu-ray.
So... is there a ranking on DVD/BLu-Ray sales by title?
I bet that "Gone with the Wind" (I bought it for my mother who only ever watched it once) is NOT in the top 200 in DVD sales.