Is there any way to get the results of Wordpress websites only on Google search?
For eg: a query or something that we can type in google to retrieve the list of Wordpress websites?
maybe try searching for: query & "wordpress"

++++++++++++++
list of top cheapest host http://Listfreetop.pw

Top 200 best traffic exchange sites http://Listfreetop.pw

free link exchange sites list http://Listfreetop.pw
list of top ptc sites
list of top ptp sites
Listfreetop.pw
Listfreetop.pw
+++++++++++++++
 
2$/Article For Your MONEY SITE! Native English Writers! Review Copy For Everyone!?
maybe try searching for: query & "wordpress"
Won't get that desired results, For eg restaurants: "Wordpress" is returning results that offer restaurant themes in Wordpress. 

I was looking for a much clearer option, something like, google returning the websites which are built in Wordpress for a particular niche or a country. Seems like the search itself doesn't have such an option.
You need a different "dork" . Try this one: 
You need a different "dork" . Try this one:

"index of" inurl:wp-content/"
Cool, that works out like a charm. 

Any suggestions on adding a niche with the search, for eg: education, business etc.
Cool, that works out like a charm.
That won't work if you need to filter out niches.
Essentially what he is suggesting is looking for all the sites in wordpress that have not restricted the directory listing in their web server.

But you are going to get only web directory listings with no content to be indexed at all, therefore, no niches or anything like that will be able to be filtered out

It's really difficult of find wordpress made sites, if they don't have some type of footprint like "Made with Wordpress" which will hardly be ever the case in top sites. Some shitty sites, may have the classic copyright footer of the theme, like the ones with the core themes or the ones with generatepress:

ojooo.com
4 domains of development
host 5 rencah 5 rasa
azobux.net
hosting 0fees
www.silverclix.com
chihuahuahits.com

Code:
"powered by generatepress"
You can always select a niche like "football" from there with something like:

Code:
football "powered by generatepress"
If you are fine with the classic wordpress web 2.0 site you can search for:

Code:
site:*.wordpress.com
If you need certain niche you can do for example (football is the niche)

Code:
football site:*.wordpress.com
Not sure if there is a way to make it work in the way you need it.