I like the way you analyze the whole issues in your comments but I will also like to know the other two clubs alongside Barcelona as the biggest clubs and the basis in which you rate them. Moreover, I don't think any sane and experienced football fan would rate Liverpool ahead of Barcelona despite the recent challenges they are experiencing. Actually, Barcelona performance has depreciate but not to the extent people are assuming it.
The biggest clubs in the world currently are Real Madrid, Barcelona and Bayern Munich.
A lot of things are it into consideration, it's not just about what they are. Achieved in recent years but they are how they've dominated the sport for a specific period.
The two undisputed top teams in the world are Real Madrid and Barcelona. Their option is open for discussion. It could be between Bayern Munich and Manchester City, but I'd pick Bayern Munich.
I see no reason why Liverpool should be rated above Barcelona like I don't understand the aspects of the ratings because if we check from league titles, Barcelona have won a record of 27 la Liga trophies and 5 champions league cup to their name whereas Liverpool have won 19 premier league trophy and 6 Champions league victory so with this statistics, you can differentiate between the both clubs and however.
The question is not who is a bigger club overall, Barcelona is obviously a bigger club. The question is which club has been more successful in the past 10 years. I know the more successful club is Barcelona, but you'd be surprised at the amount of fans that'll pick Liverpool.
This is because of hat Barcelona has done in the past 10 years looks like child's play compared to what they used to be but if any other team achieved that, the club would be applauded, that's why I used Liverpool.