Cyclops hasn't really changed that much. He's just become a bigger dick.
How are any decisions he makes now different to what he would've done 20 years ago?
Cheating on his wife? Did that now and 20 years ago.
Fighting with Wolverine? Did that now and 20 years ago.
Being a dick? Did that now and 20 years ago.
EDIT: So I was looking stuff up on Wikipedia and I had completely forgotten about this:
Scott and Jean return to the X-Men some time after at the request of Storm, when she grows concerned about the mental well-being of Professor X (who had returned sometime prior).[volume & issue needed] Their return then leads to the events of The Twelve, in which Apocalypse plans to use a machine to steal the powers of twelve select mutants and the body of Nate Grey which will make him virtually omnipotent.[volume & issue needed] In order to save Nate, Cyclops willingly merges with the villain Apocalypse. He is believed dead until Jean and Cable track him down to Egypt and separate him from Apocalypse, killing Apocalypse's spirit in the process.
Upon Cyclops' return to the X-Men following his possession, his personality has been altered as a result of being bonded with Apocalypse. This change causes a rift between him and Jean; he claims that Apocalypse made him question not only their relationship, but his life as a whole. He is instrumental in preventing the mutant Xorn's suicide and in recruiting the powerful mutant to the X-Men. The two establish a close friendship; similarly, repeated missions with Wolverine result in the growth of a tentative friendship between the two veteran X-Men.
When Jean begins to show signs of the Phoenix Force again, the distance between the two grows larger and Scott begins abstaining from sex with Jean for the five months. Jean attempts several times to confront Cyclops, but he continues to push her away, claiming that Apocalypse had changed him too much on the inside.
He is so totally a villain now. I had completely forgotten about that.