The NCAA men's volleyball statistics site (see links column to the right) provides an aces-per-set statistic. Aces are only one part of judging serving ability, in my view. Someone might be able to amass a large ace total by attempting extremely hard jump serves at every opportunity, but such aggressive serving likely would also lead to a high rate of service errors. Another aspect to consider would be serves that, while not aces, still took the opposing team out of its offensive system. Only aces and service errors are listed in publicly available box scores, however.
What I did, therefore, was find out the top 10 players in serve-per-set (through matches of March 30) via the NCAA site. For these players, I looked at their ace totals (from the NCAA site and the players' respective school athletic websites, using the latter in the event of slight discrepancies) and their service-error totals (available only from the school athletic websites). I then plotted the 10 players' ace and error totals (using this plotting website). As shown in the following graph (which you may click to enlarge), aces and service errors are positively correlated (r = .34), which means that the more aces a player serves, the more errors he serves. The upwardly sloping red line in the graph illustrates the trend.
The best serving is thus depicted in the lower-right corner, highlighted in yellow. Players in this area of the graph served large numbers of aces, but had far fewer errors than would have been expected based on the trend line. The blue arrows below the trend line indicate the top servers, the further down the line drops, the better. Using this approach, my top three servers are:
1. Gonzalo Quiroga (UCLA), who served 47 aces with only 60 service errors. By comparison, Lindenwood's (Missouri) Colin Hackworth also had 47 aces, but committed a whopping 114 errors. Relative to the trend line, Quiroga had roughly 20 fewer service errors than would have been expected.
2. Aaron Russell (Penn State), who recorded 44 aces with 61 errors, who edges out...
3. Loyola's (Chicago) Joseph Smalzer, who aced the opposition 51 times, while committing 71 service errors.