for example a site called realestate.com will come on top for the kyeword real esate even if the domain has less back links. not realestate.com it has lot of back links. I am just taking an example thanks
I think that when there's a good site using the keywords and a .com it automatically gets ranked higher.. not sure if this is really true but it certainly looks like it.
Google uses keywords in the domain as part of their algorithm - whether the TLD is .COM or an alternative shouldn't matter.
I also noticed this, and it usually happens with .com or with the extension of the country in which language the keywords are