Best newcomer is El Guapo, downtown. Owned by the son from Nelson's (long since closed), who also owns McNellies (great burgers & beer, also downtown). Definitely worth a visit.
I tend to stay away from national chains. Best "local" chain is Mexicali, with several locations (downtown & also 71st & Sheridan are 2 I've frequented).
Senor Tequila's is another "local" chain, which has a couple of locations in town. Mexican owned & operated; you'll find Mexican soccer on TV in the bar all the time.
I used to go to Chimi's a lot, but got tired of it even tho it's only 2 blocks from my home. I'm sure it's still pretty good, just hasn't changed probably since you lived here (except it did move to the corner of 15th & Peoria since you were last here).
All the above have very good food & it's hard to mess up a margarita so long as you get one with 100% agave tequila.