Muslims adamantly say no but provide no proof. And say Christians altered scriptures. Was the man actually crucified?
Most modern scholars (historians of early Christianity) thinks that Jesus existed and was crucified. The same historical proofs which are used to argue for the historicity of Jesus is the is also used to argue that many of the elements described concerning Jesus life is historical and also the crucifixion.
One historian muslims like to quote is Bart D. Ehrman (an apostate of Christianity, agnostic now). If you look at 'muslimbychoice' at youtube's different historical documentaries (which by the way is illegal uploads) Bart D. Ehrman is a central figure used to back up the claim that the Christians altered the scriptures (and to spoil it all they really did so, but it was not an unussual allegation against the 'Christians'. Different groups (or sects) of Christians accused other groups (or sects) of Christians of doing this; Mani the 'seal of prophets' in Manichaeism accused the Jews and the Christians for altering their holy books (he even criticized Moses and Jesus for not writing their message down themselves, and so Mani did write his holy message down himself), different Latin and Greek Roman pagans accused the Christians of altering their scriptures and so forth). Now Ehrman is also an fervent defender of the historicity of Jesus and the crucifixion of Jesus.
Different opinions concerning the historicity of Jesus is introduced on this site:
Historical Jesus Theories. Wikipedia's page on the
crucifixion of Jesus is basicly presenting the majority of the scholars opinion.