This is one of those recurring theme questions
.org Has only limited application because ,despite open registration people still regard as organisation only'
.net Has only limited application because ,despite open registration people still regard as Network only'
.biz Great For Money-Making or Marketing sites
.info Informational site is what the Internet is all about, Google LOVES Content sites and .info is IDEAL for these.
My rankings
.INFO Number #2 Behind .com
.ORG .NET .BIZ #3 Equal (each has a Different ,but VALID Niche)
Value of ALL gTLD's is always based on Need . Therefore Value for any these will depend solely on it's validity of usage and Fitness for the application
for example
.org is always valued higher than a .biz for a Charitable site
.biz will fetch more than .org for a eBOOK marketing site
So it is hard to say a Particular gTLD is worth more than another one.
But all TLD's Have their place.
Spend more time using ALL of them .
Spend less time analysing,Discussing,arguing about which is the supposed BEST to use.
Whatever you do don't just ignore them ,because while .COM may be the most popular, it is not the ONLY choice