The effects aren't better, though. In Star Wars, TIE Fighters now look like shiny plastic, and Jabba the Hutt looked so unrealistically and comedic it's unreal - much different to the menacing revulsion Jabba carried in Return of the Jedi.
It's not about being purist, as much as the fact that classics are classics, and should be left that way. It's rewriting history otherwise.
Imagine if a ghost-written novelisation of the Peter Jackson movies was the only version of Lord of the Rings that would ever be released - with the original Tolkien burned. Wouldn't that be a good idea? After all, the films made far more money than the books, so surely that justifies it?
The CGI'ed Star Wars versions are not the classic movies we saw as kids. The arrogance of the man dumping those horrendous prequels on us, then changing the original movies, is appalling.
A choice would satisfy me. In my opinion, Lucas is simply going to stoke a strong pirate market for the originals by insisting consumers only have access to the inferior later editions.
Lucas may think he's completing a vision - but as history has shown, Lucas needs strong criticism of his work to make it adequately strong. This is precisely what seems to have been lacking in his more recent work - hence why the sycophants he obviously works with having not protested any of the awful decisions he's made since returning to the sreen.