So while the fighter isn't always going to lose, the deck is stacked against him vs spellcasters.
I don't think you have proven this completely. In this situation, yes, the deck is against him. How many encounters take place in these situations?
Who has a better chance in this fight:
Fighter v. 3 mooks or wizard v. 3 mooks
And lets assume the mooks don't just stand in a nice triangle/square for the wizard to hit them with colour spray or sleep...
The point is - you can craft any situation to be more beneficial to one character or another. That has nothing to do with balance.
The point of the game system isn't to balance a character class - it is to balance a party. A balanced party has various roles filled. Sometimes a class can dip into another role to vary the flavour, but it doesn't mean that the class is now "unbalanced."
I still don't understand why this is a competition between whose class is better - they are different. That's all. They are supposed to be greater than the sum of their parts as a party.
As GM, I could have you make any character you wanted to - and I could either kill your character by deigning an encounter that wasn't suited to you and that you couldn't possibly overcome on your own, or I could make an interesting story that played to your strengths and challenged you in fun ways that you could overcome with some ingenuity.
Don't blame the player or class if you can't make an interesting and challenging story.