The canonical Christian teaching is that He truly died. Or at least His body did, while His soul "descended to Hell" where He proclaimed victory over sin and Death itself (search for "Harrowing of Hell" for details, however little is actually said about it in the Bible itself).
(Some interpretations believe that through this act he also "opened the Heavens" and liberated all the righteous that died before him.)
He then resurrected Himself (being part of the Divine Trinity and all) as a divine act (further demonstrating His dominance over Death), and eventually ascended into Heaven, body and soul, but that, I believe, is out of scope of your question.
TL;DR: Canonical Christian belief is that Jesus really died by crucifiction, entered afterlife, defeated Death, resurrected Himself, thus completing His mission.
and quick and simple rhetorical question:
Who would like to trigger a new "religion" about six hundred years later, in which he was not able to deny Jesus' presence, but at least tried to: deny of well proven historical fact of his death by crucifixion and this way to indirectly nullify all other things described above?
reply
hint: "There are 666(6) verses in the Qur'an."