I looked up the players' activity so far and the guy with the most wins - and matches played overall - this year is Javier Genaro-Martinez (ESP, #299) with 25 victories and a PCT of .806. He's been playing all the Spanish futures (1, 2, 3, 5, 6, 8, 9 and currently 10) winning one and making it to the finals in 4 others.
Adrian Menendez (ESP, #357) who's had a little less good luck is also on the same circuit and is not too far behind with 14 wins and a .667 PCT.
Interestingly, there were 47 Spaniards competing at the beginning of this week, which is below the 57 Frenchmen and above the 35 players coming from the USA, Germany or Italy.
Yes, in any given year the top 10 matches played list will be filled with 2-3 Spanish futures players. Last year it was:
1. Mischa Zverev (GER) 74-31
2. Benjamin Becker (GER) 70-30
3. Juan-Albert Viloca (ESP) 66-34
4. Gorka Fraile (ESP) 61-39
5. Lukas Rosol (CZE) 69-30
6. Alberto Francis (USA) 65-34
7. Andrey Golubev (RUS) 63-36
8. Nikolay Davydenko (RUS) 69-29
9. Simone Vagnozzi (ITA) 66-32
10. Roger Federer (SUI) 92-5
Players like Viloca and Francis took advantage of the four-round futures qualifying that is more prevalent in USA and Spain futures. A few other Spaniards Pablo Santos-Gonzalez and Jose Checa-Calvo were in the running all year before dropping off at the end.
Also, while the ATP site is miles better than it was years ago, it doesn't include any qualifying matches at any level. Steve G's site ranks players by matches played and winning percentage...taking qualifying into account and not including this week:
1. Vladimir Obradovic (SRB) 24-8
2. Justin Diao Natale (USA) 24-7
3. Javier Genaro-Martinez (ESP) 24-6
4. Peter Polansky (CAN) 26-3
5. Dusan Vemic (SRB) 20-8
6. Ignacio Coll-Riudavets (ESP) 18-10
7. Edouard Roger-Vasselin (FRA) 18-8
8. Carlos Poch-Gradin (ESP) 18-7
9. Fabio Fognini (ITA) 16-9
10. Miquel Perez-Puigdomenech (ESP) 16-9
Javier Genaro-Martinez is 27, so he doesn't have much of a future, although he has had a good year so far. Adrian Menendez, as you mentioned earlier, is also having a decent year and is 21, so he has a bit more promise. The best prospect with a ton of activity is Peter Polansky though...he's the infamous junior who fell out of a third-story hotel window, but recovered and is now looking like one of the better young players currently on the futures circuit.