El Mariachi is one of Robert Rodriguez's first movies. Done on a budget of about $7000 it has some pretty cool action scenes and a good plot line – 3/5.
Desperado is my favorite of the three, this has heaps of awesome gunfights and lots of explosions – 4.5/5.
Once upon a time in Mexico is the ending to the saga, it has a few famous faces and a big Hollywood budget. A couple of good scenes with a feasible story line – 4/5.
Overall a good box set:)
Highly recommended.