Not gonna lie.. I'm 30 and I STILL watch Power rangers.. always been a big fan, mostly because I've always been a big martial arts enthusiast.
i don't think any cast really captured the variety like the original, with their different fighting styles and personalities: Jason, the stalwart, gruff leader, Billy the genius gymnast, and the break-dance fighting style of the Black Ranger although the following black ranger was a true practitioner of kung fu and now does straight to dvd action movies which aren't half bad. Jason David Frank the original green, then white, and eventually red ranger, after reappearing in a the DIno Rangers series as the ass-kicking mentor (and apparently the last surviving original ranger according to continuity, excluding that awesome episode "Forever Red" which reunited all of the past and current Red Rangers in the 500th episode) has gone on now to MMA fighting, which will be interesting to see...
The fact that they also tried to give the city itself life, which is interesting in that the residents of Angel Grove seemed incredibly resilient considering that every other day or so their city was being ravaged by giant telephone booth monsters knocking over buildings and what-not.
I think Power Rangers always had the potential, if taken more seriously, and with a much higher budget to be on something like Sci Fi channel.. an hour long show, filmed in the style of battlestar galactica.. how awesome would that be? Toss out the "fight puddies, fight random birdhouse monster, fight enlarged monster in mech" formula and concentrate on stories and special effects and you'd have something very entertaining, especially if you include smart writing and depth. I think it could be done... look at Iron man.