When I used to play RPGs as a young teenager (and, later, in PBEM and PBP iterations) the idea was always to come up with a PC who could essentially be the main character of a novel. They had backstories, they had detailed appearances, and they had personalities. "He's witty and incisive!" "She's grim and brooding!" "He's eccentric and strange!"
I understand that this is as big an element of the hobby as it ever was, perhaps more so, and that in fact creating interesting PCs is a significant chunk of the fun of things for a lot of people (indeed almost a hobby in itself).
The problem that I always encountered was that the PC as envisaged by the player during character generation is often a very different beast to that which emerges at the table. Put bluntly: maybe your PC as you imagine him is witty and incisive. But maybe you can't pull off witty and incisive. Maybe your PC actually comes across as a boorish, overbearing idiot.
I would like to christen this the 'Patch Adams Problem'. Have you ever seen Patch Adams? Don't. While it is not perhaps the worst film I have ever seen, it is offensively bad, the least desirable kind of bad, not so bad that it's good, but so bad that it makes you feel a worse person for having watched it. Peter Sellers is once said to have replied, after being asked whether he would do anything differently if he could live his life over, "I would do everything exactly the same except I wouldn't see The Magus." The experience of watching Patch Adams reminded me of that.
The film has many flaws. But at the heart of its badness is the character of Patch Adams himself. The creators of the film envisage our 'hero' as funny, intelligent, kind, beloved by children, esteemed by his peers as a charming eccentric, and filled with an optimistic passion to help others. And that is indeed the person that the cast of characters seems to be reacting towards.
But this is not what we, the audience, see. What we see is actually an unfunny, obnoxious, creepy, lecherous, leering, sanctimonious, belligerent oaf, perhaps actively malevolent, but certainly narcissistic and blinkered, and bloody-mindedly focused on pissing off everybody around him for no good reason whatsoever. The film is littered with arguments between himself and others, and in almost literally every single one of these disputes, we find ourselves agreeing wholeheartedly with whoever Patch Adams is arguing against. Yet at the end, it is he who triumphs. It is a bit like a filmic version of A Confederacy of Dunces, except nobody who made it is in on the gag.
The point, of course, is that if you are going to pretend to be a funny, intelligent, brooding, menacing, insightful, charming or creative character, you had better actually be funny, intelligent, brooding, menacing, insightful, charming or creative when in character. And the one most certainly does not necessarily follow from the other.
The approach which old school play tends to favour, and I think by far the most sensible, is to begin as more or less a blank slate. One can paint in broad brushstrokes, certainly at the physical level. And the PC's stats may suggest lack of intelligence, a muscular frame, etc. But it is best for the PC's personality to emerge as you get to know her, and as events shape her. Often, it will turn out that her personality is a lot like yours. But at least if it is she will seem like a genuine person and not a poor copy of some figment of your imagination.