Denzel has said the third one was his last. I rank them as 3, 1, 2 in order of preference, but that's just me. I liked them all a lot. I really liked
Man on Fire, which is very similar in nature. One of my favorite Denzel Washington movies, and I like a lot of them. I used to watch the original TV series with Edward Woodward. I thought it was good at the time, but I like Denzel better, plus the action is more serious.
There's even an Equalizer TV series with Queen Latifah. It seems ridiculous, but I actually enjoyed watching it. She did a decent job.
Some prequels to the Denzel movies could be awesome, when he was at the peak of his killing skills. Along the lines of
Mission: Impossible and James Bond. A CIA assassin series.