What makes a website realy great?

I think that one of the first things that people look at is how professional a site looks.  It a site looks sketchy and put together in a sloppy fashion, people will just close the site and open up something new.  There is almost no idea that more that one person hasn't thought of.  You can always find a different site if you don't think the site is user-friendly.  Especially, if you ware selling a product, trust needs to be built... and believe it or not, this is done by the appearance of a web-site. 

Yes, of course good content is essential... good traffic will come if you have a quality site.   

I think that content is probably the most important thing, I've seen great looking sites who had nothing interesting in them and never went back, however some of the sites I go back to over and over again, cause I find the information or images in them useful.

UI, Design, graphics and so on are basically there to support the content.

I have avoided useful sites because the design was bad, but if the content is really bad or unuseful or boring, no great design would save it.

Saying this I think that the boundary between content and design is not always clear and that it's basically a combination of all of the above.

traffic came from good content and good content can establish or form a good source from search users.

to have a great website. the website must be informative and detailed. not that traffic and it must not contain PPC (Pills,Porn,Casino). it can be called great if may find it interesting and they may not get bored. to have a nice content of the website you are making of. you must hire a website content writing services so.
so people may not get bored reading articles or any of the content of your web

The one that is having an interesting content in relation to what they are looking for, that might caught peolple's attention and stay with it. Traffic plays a good role if it has a good traffic, many will be hooked into this site also.

To get a good website check this site out, http://www.helpfulguy.com/, this will give you more loads about search engine optimization and other useful strategies.