Too many variables for me to answer the poll in a meaningful way.
Does the portfolio include the value of real estate, i.e. are we to assume that the living expenses need to cover a mortgage or rent, or are those expenses eliminated by a paid-off home?
Do you want to pay for your children's undergraduate education, or do you want them to pay for it on their own? Do you want to finance advanced degrees for them as well, or do you draw the line at undergrad?
Do you live in a place where you're happy with the public schools, or do you want to send your kids to private school for some reason (religious preferences, etc.)?
How far do you need to travel to visit family, i.e. are annual trips abroad to visit close relatives "back in the Old Country" important to you? Or are large travel expenses more discretionary?
Do you really, truly plan on never doing paid work again? Or is the FIRE plan more along the lines of stepping off the treadmill, quitting the rat race, and maybe finding work or a small business that you enjoy and can do on a part-time basis?
Are you healthy enough to obtain private medical insurance at a reasonable rate, or do you have an existing condition that would make it much more expensive?
And then, of course, there's the basic question of what material lifestyle do you want ("need") ... keeping in mind of course that even the lower middle class American lifestyle is far wealthier than the vast majority of the world's population.
Depending on all those variables, I could see 0.5 million being enough for some, and 5 million not being enough for others.