It feels a little strange to discuss this kind of topic. The argument could be made that during the initial period of conflict that there was not too significant a difference in overall talent, in the long run the available pool that the factions could draw on were limited. I believe it might be a good idea to discuss three different eras of military strategists: The initial free for all, the consolidation, and the regression. The time from He Jin to Emperor Xian fleeing East was a period characterized by chaos, and the forging of short term alliances. Talent here was mobile, and even brilliant men could be snuffed out due to the wanton nature of the conflicts. When there was an opportunity for talent to shine, it did, but most others were looking for positions where they could employ their talents, or even just survive.
The second period of consolidation occurred from Emperor Xian's establishment in Xu to Cao Cao's withdrawal from Southern Jingzhou. This was a time period of emerging stability, and talented people ceased to be mobile. While individuals could bounce from place to place before, after this strong personal ties of loyalty tended to be formed. Cao Cao was able to swallow whole the North and incorporate talent into his reemerging Han, while those who fled found themselves in the service of only a handful of leaders who could resist. Sun Quan primarily, who then went on to establish a pseudo-colonial empire in Southern China, presiding over a demographic revolution talked about in Generals of the South. Liu Bei was an auxiliary who attracted significant attention, but seemed mostly to cannibalize other leaders not under Cao Cao's direct leadership.
The third period lasts until the Jin reunite China, and is a regressive period. There are defectors, but talent largely becomes completely immobilized. The older guard dies off, and it is their children and the people produced from their controlled territories that have to take up the reins of leadership. In this stage, Wei was always going to win. The longer the scenario was perpetuated, the greater the share of talent would be funneled into the north as they had a massive demographic advantage. Should one looks at the institutions and practices that give rise to talented men, as a means to compliment or compensate for demographics, the clear precedent remains with Wei. There were talented men in all of the factions that remained, but the regression to local predominance leaves much to be desired. It was defectors from Wei in Liangzhou that would provide several key members of Shu-Han's last generation of military leaders.
Really, the closest the powers were to being equal would have to be the consolidation period. Before that, there was too much uncertainty with people predominating over faction. Afterwards, there were limited means of attracting and producing talented individuals.
Of course, this just seems to be an impression I've drawn. Feel free to showcase anything I've missed!
Alone I lean under the wispy shade of an aged tree,
Scornfully I raise to parted lips a cup of warm wine,
Longingly I cast an empty vessel aside those exposed roots,
And leave behind forgotten memories and forsaken dreams.