That's a big subject! Shall we begin with Villa-Lobos or Rodrigo? Have a look at this: http://www.musicated.com/cgcl/music/CGCL_chron.html
It might be subjective but here comes my "majorcomposers list" chronologically(looking through the musicated list, which doesn't include everyone): Rodrigo, E. Sainz de la Maza, Santorsola, Gnattali, Asencio, Holmboe, C. Romero(?), Guastavino, Ohana, Garoto!, Smith-Brindle, Lauro, L. Almeida, Carlevaro, Duarte, Piazzolla, Henze, Takemitsu, Nørgård, Abril, Ruiz-Pipo, Baden-Powell, Nobre, Towner, Gilardino, Marco...wow...no Leo Brouwer on the list?? That's my small start. Maybe someone can shorten it alot!
I left out big names that only have written 1 big piece, like Britten f.ex.