I always play wizards in RPGs, and I was surprised to see the other day that Fable 2 has no mana at all. There's charge times, and that's it.
And as a wizard, that's the best thing I can ask for a magic system.
If the warrior can swing his blade endlessly, I want endless fire balls. I don't mind them doing little damage, I just don't want to keep drinking, reading, being limited to X times a day or having to do math so I can do more spells with the same MP. That's why, as much as I loved Baldur's Gate 2 (which I bough after comparing which RPG at the moment had more spells), I will always be marked by the distracting and ilogical times I just shut a door behind an enemy so I could sleep and recover my spells.
"But some magic powers are too powerful!"
Well, warriors have special attacks too. I'm not saying asking to be able to spam my Kill-O-Matic spell, and that's why my vote goes to mana regeneration. It find that kind magic fatigue system the most natural for gameplay. But it's my wizard heart speaking.