Having a discussion with a friend about which club is bigger, Spurs or Celtic. I would say historically Celtic, but if we take a snapshot of the clubs at this moment in time I would say Spurs.
I would say not to underestimate the global fanbase of Celtic but I think they are not on the level of the premier league’s current elite due to the vast fortunes that have been accumulated in recent years by the PL’s biggest clubs. I think there is a yardstick for comparison with the tier of clubs just sitting under the true elite of Liverpool, Man United, Woolwich, Chelsea and, perhaps latterly, Man City. Hypothetically, a share of PL TV money and Celtic would, in my view, challenge the top eight fairly consistently after a season or two (not that that scenario will arise!)
Celtic
Won the CL, first British club to do it
Dozens of league titles, cups, etc
Far more silverware (in a less competitive league)
Huge global fanbase
Passionate support - would take an amazing away following anywhere
Had a lineage of incredible players on their books, historically
Spurs
Did the FA/League double in ’61, first English club to do it
Massive global fanbase, esp. in Asia - (see Son Heung-Min)
Arguably best stadium in Europe
Arguably best infrastructure
Reached a CL final last year
Squad full of superstars, one World Cup winner
Celtic 5th, Spurs 6th
The 50 Biggest Football Clubs in Britain - Ranked
Spurs 6th, Celtic 8th
Top 30 biggest football clubs in Britain - counting down from 30 to number one
YouGov lists Rangers above Celtic, quite surprisingly to my mind
The most popular football clubs in the UK | Sport | YouGov Ratings