My top 3 (Estrada-Rivero, Escalante-Roman and Cazares-Nashiro - round 12 is probably my round of the year so far) have already been mentioned, but the best fight so far that hasn't been mentioned in this thread is Juan Alberto "Topo" Rosas vs. Simphiwe Nongqayi. Domestically, Burns-Martinez was probably the best so far, but I also enjoyed Munroe-Terrazas and Bayaar-Sexton.
Probabily go for Mares v. Perez as well. The right mix of skill and back 'N' forth action. It had a layer to it.
This :deal Nashiro vs Cazarez II is the stand out of the year so far, by a mile. Froch vs Kessler was sloppy ****, I'm sorry but I thought it was crap.