For quality I'd put LOTR above SW OT. But if I had to make a "desert island" selection then nothing tops SW.
Hmmm interesting.. I get where you are coming from and I think 10 years ago I would have agreed.
But now I really don't think the quality of LOTR is better then ANH. I really don't think its as good as ESB.
LOTR is great and I love it but IMO they have lost some of their luster and have not aged as well. However FOTR is still the best of the series IMO and of the three films it has aged the best... ROTK has some great moments but it has some of the series worst.
Now ROTJ brings down the quality of the OT series for sure and TTT does not bring down the quality at all as far as film making goes. So I guess as a full series you have to say LOTR is better quality. But ROTJ is a better movie then TTT to me. As I mentioned before Jedi has great moments. Some of the best in the series. TTT offers nothing but Golum. Story wise its a bore and it offers the worst action set pieces of the three films IMO.
Again I still love LOTR... But I just watched the films again a couple of weeks ago and was a bit board by it all and found some parts very cringe inducing.
As for dessert Island. OT rules over all film series.