I don't want to start a debate here but want to make few things clear.
"In the late '90s and early '00s, a wave of films played with the notion that what we experience as reality is a false and perhaps malevolent illusion. The idea wasn't new -- it was at least as old as Plato, and it had provided the backbone for many movies already -- but suddenly it was everywhere: in The Truman Show (1998), Dark City (1998), The Matrix (1999), the Canadian eXistenZ (1999), The Thirteenth Floor (1999), the TV series Harsh Realm (1999-2000), Waking Life (2001), Vanilla Sky (2001), and others. The broader idea of prowling about in someone else's virtual world turned up in still more pictures, from What Dreams May Come (1998) to Being John Malkovich (1999) to The Cell (2000). The quality of the films varied widely; the idea at their core did not.
You can credit part of this glut to imitation. But too many of the projects were created simultaneously and independently for that to explain everything. For whatever reasons, audiences at the turn of the century were receptive to paranoid thrillers about inauthentic realities. Call it the demiurge cycle, after the Gnostic notion that our world is governed by a mad ersatz God."
Source:*www.reason.com/news/show/29028.html
So, the core concept is same.I agree with that.If you dissect each and every movie,all you will get are handful of concepts told differently.
You can't call The Matrix as rip-off.It really deals with greater issues than dark city.It borrows inspirations from many things like from books like 'Simulation & Simulacra'(It was given to almost every actor to study),different religion's philosophies,animes like 'Ghost in The Shell' and even fairy tales like 'Alice in Wonderland' and 'Looking through the glass'.Wachowaskies have paid tribute to their inspirations wherever they can(Book used by Neo to conceal disks is simulation and simulacra,Broken Mirror is reference to Looking throught the glass,white rabbit tatto)
Here is something more about this:*en.wikipedia.org/wiki/Influences_and_interpretations_of_The_Matrix
Also,The Matrix was released one year after Dark City and was also filmed at Fox Studios in Sydney.(*en.wikipedia.org/wiki/Dark_City_(1998_film)).
The rooftops that Trinity runs across at the beginning of the film are the same ones that John Murdoch runs across in Dark City.(*www.imdb.com/title/tt0118929/movieconnections) ,The rooftop set that Trinity uses to escape from Agent Jones early in the film was leftover from the production of Dark City, which has been remarked upon due to the thematic similarities of the films. (*en.wikipedia.org/wiki/The_Matrix).Which means that creators were aware of thematic similarities.
Also,their release dates are barely one year apart(Dark City:USA 27 February 1998 and The Matrix:USA 31 March 1999).So you want to say that Wachowaskies watched dark city,decided to copy it,thought about how to fool audiance by making changes,finalize actors,start filming,finished it,then completed post production in just one year?Come on guys,the training for kung-fu alone took few months.
And even after 10 years of release,there are hundreads of sites,forums,communities and groups discussing The Matrix.So,if you still think it was just a simple action movie and did not made you think,please don't say that out loud in front of any Matrix fan.