Charapedia asked 10,000 anime fans the question: Which supporting male characters would you like to see as the protagonist? And from thousands of fans, most of the responses are from the female fans (54.1%), male fans (45.9%) and teens to their 20s (79.3%) while the other 20.7% are 30 and over.
Fans also voted for female support characters which can be seen here.
Here are the results:
20) Shogo Makishima (Psycho-Pass)
19) Shuu Tsukiyama (Tokyo Ghoul)
18) Keigo Atobe (The Prince of Tennis)
17) Itachi Uchiha (Naruto)
16) Portgas D. Ace (One Piece)
15) Accelerator (A Certain Series)
14) Kei Tsukishima (Haikyuu!)
13) Rin Matsuoka (Free!)
12) Izaya Orihara (Durarara!!)
11) Mikoto Mikoshiba (Gekkan Shoujo Nozaki-kun)