Greetings!
Indeed, Belisarius was a brilliant general, and Narses was a good commander, too. As for generals in D&D, well, I give all classes a bonus of +2 skill points per level, because the skills as stated really don't allow for much depth for any character.
How rounded and deep of a character can you have with a fighter who only has climb, ride, swim, and jump as significant skills?

Part of the problem is that D&D is designed as a default assumption of a Hack & Slash game, thus everything, especially the skill ratios--are designed to pre-channel, and keep your character into a very narrowly defined character type--which, regardless of specialty, whether fighter, wizard, or cleric, is still primarily geared for Hack & Slash, and little else.
It is difficult to make whatever characters--but fighters especially--into well-rounded, deep characters, with many different skills and specialties, from perform, to History, to the skills necessary for being a General.
I also use the skills found in Kalamar's Player Guide, which has skills tailored for Generals. With the increase in skill points, this is a partial remedy. I also think providing a broader subset of skills classified as "Class Skills" is useful for all of the classes, as there is a bit broader range of skills available now than in the beginning, and there is a need. I am also considering jumping the skills from a bonus of +2 per level to +4, because I still believe that there are characters that unless they have unrealistically high intelligence scores, they don't have enough skill points to effectively "know" what their character's should "Know". It becomes somehow artificial to feel like every character, regardless of class, must have a 22 Intelligence or higher in order to have the skills necessary for a well-developed character.
For example, in my campaign, there are perhaps anywhere from six to a dozen knowledge skills that *every character* really needs. I have characters often interacting on their own, getting involved with other things, and they don't always travel everywhere as a group, nor can they point to one character and say "He's the Bard, or she's the rogue, you do all the talking!"
It just doesn't work that way in my campaign. There is a broad need for different characters to have knowledge in History, Local, Streetwise, Law, Literature, Religion, and Perform, for example, in addition to Diplomacy, Gather Information, Bluff, Spot, and Listen. Almost every character could use from 6-15 skill ranks in just about every one of those skills. Indeed, there is a lot of combat in the campaign, but when *not* in the dungeon, or out in the wilderness, these skills often come in regular and frequent use for every character.
Fighters, especially if they are to be generals, they need some help in the skill department, as well as a high charaisma score. Providing those things, as well as a good reputation, then the character may well have an army of warriors following him into battle!
Many generals are indeed aristocrats initially, but not all. In fact, before the rise of Fuedal Europe, the "Aristocracy" were not aristocrats at all, but merely rough, hard men who managed to have armor, horse, weapons, and greater skill in combat than most of their neighbors. These were the beginnings of fuedalism, and the people who would gradually lay the foundations for all of the "nobility" two to five hundred years later.
That in mind as inspiration, plus there are other examples throughout history, of common soldiers or barbarians rising to the positions of leadership to lead armies into battle, so I don't see an overwhelming need for all such generals to be aristocrats.
I might also suggest that for those interested, that they think about customising a prestige class that includes a large skill-set, plenty of skill points, and other neat abilities to reflect the skills and abilities of a general. The game doesn't really have good examples of this, so it would take a little work on the part of the individual.
Hail to the Conqueror!
Semper Fidelis,
SHARK