What are the best topics for blogs in your opinion ?  

i think it`s about online business or about love or friendship

Selecting topics based on very popular keywords is not necessarily the best approach. This is understandable because there are also a lot of competition for those keywords.

To select a good topic, use Google's keyword tool and find a keyword with reasonable traffic, but less competition. You will have to determine the appropriate balance.

https://adwords.google.com/select/KeywordToolExternal

its always best to blog what your interested than what the others are. people like the site only when they find information about which they don't know and are looking for.

I am having a site & 2 blogs, my site is about online earnings and one blog is for home jobs and another is for interesting informations, i promote my site and blog in traffic exchange and get a nice traffic to them. I provide the details in my profile. I think online earnings are the best topic for blogging. All the best.

I think the best topic and the most sought after topic for blog is, "How to generate traffic for your blog". If you are caught in the middle of nowhere trying to find out ways to increase traffic to your blog, chances are there are many bloggers out there who have the same problem as yours!

It has to be something you yourself are passionate about. The quality of information will show if you like what you do. But if I were to make a blog, I would want it to be a travel and food trip blog. I would want my blog to be a good read for those who want to go backpacking and for those who would want to have some fun, unwind and explore the beauty of the world without compromising their budget. I would indicate there how I got there from a certain place, how much each mode of transportation costs me to travel from one spot to another, how much I paid for food, what meal I had and for how many people the serving was good for and if I liked how the meal was made. I would also include a number of lodging houses, their costs and how to get there for my readers to have options. And then how can I forget the beautiful spots a traveler should not miss if they will ever go to that place. I will include how much I paid for a certain mode of transportation for me to get there, how much they will save if they go in groups and the best and most important stuff to bring if they'd go there. I would also include any historical background of that place for them to understand how important these had probably been for the people who have lived there almost all of their lives. I will never forget to post pictures or even videos for people to see and even imagine themselves being in that place. I would want to inspire them to see how beautiful the world can be and how beautiful it is!

the best topic for a blog is the one which you love most.
Yes, I am not joking. I am very serious.
You write best only when you love the topic. Otherwise, thought process takes time and words not only come out with great difficulty, but also without the passion.
This reflects in your writing and thus the quality of blog suffers.
Write what you are most passionate about.
It can be music, sports, movies. whatever it is, let it be from your heart.
Best of luck