Even though the film is shorter than Return Of The King there is a hell of a lot of plot: Chitti goes from failed military prototype to superhero to love rival to supervillain, and the film rolls together ideas from RoboCop, The Terminator, I Robot, Bicentennial Man, very heavily from Short Circuit and probably every other robot movie book or play since Rossum's Universal Robots, while adding one or two twists of its own.
Endhiran also utterly disregards Western genre conventions combining elements of action, thriller, romantic comedy, slapstick comedy and black comedy and of course musical theatre, and there is absolutely no conflict between any of the styles: you get to have your cake and eat it.
I have one complaint: the subtitles. Endhiran has the worst English subtitling grammar I've ever seen. Sorry. I'm often disappointed in fellow cinemaphiles who miss out on some great films because they find subtitles too irritating - but this is exactly the kind of thing that gives subtitling a bad name. Incidentally, and just to drive the message home, you can see the best subtitling ever in this film.
As a Westerner with little experience of Bollywood or Tamil cinema I can report Endhiran is very watchable and I would recommend it to others outside the traditional audience. It has captivating stars and catchy music, it's full of ideas whether original or borrowed and it's fun from start to finish. I sincerely hope this leads to many more Bollywood-style sci-fi epics.