Tolkien finished the LOTR as a single book, which his publisher then wanted to release as three volumes.

Then again the LOTR is also 6 books, with 2 books per volume.

Also The Hobbit isn't a prequel, but LOTR is the sequel :), and Silmarillion wasn't finished by J.R.R.

LOTR is easily one of the best written works of all time.

Haven't read any of them but judging by setting alone, I can answer LotR. I couldn't care less about vampires or a British wizard boy which alone would pretty much kill the books for me.

I prefer Lord of the Rings, but the Potter series is great, too. If I had the option though, I'd totally pick the Wheel of Time series.

True the Hobbit is not a prequel it's been a long time since I read up about the books I forgot it was written first. 

But the fact that LOTR was origonaly put forth as one manuscript doesnt change the fact that it was published as 3 seperate volumes (and the majority of the different edditions are published that way), It qulifies as a series. Tho it probably would be more accurate to refer to the LOTR as a part of the greater tales of middle earth or mythopoeia. 

Also the fact that the Silmarillion wasn't finnished by JRR doesn't really have any real importance, many series include works not from the original creator and JRR did write almost all the content (and some of it was clearly left unfinnished) so it's not like it's not his work even if he didn't get the chance to put it together himself. 

I'm sorry I'm sorry...But why the hell is Harry potter not first? HP FTW!...And twilight? Whoever said twilight please please leave? Leave the internet and never come back...NFGout!