The Turkish team boasts a good home record, losing only two of its last 14 home European matches, but Ronaldo is also in good form with 21 goals in his previous 19 Champions League outings.
Now that Ancelotti has sold Mesut Ozil to Arsenal, the German player's pinpoint passes look likely to be replaced by explosive attacking runs and fierce crosses into the box.
Bale scored in his debut with Madrid against Villarreal, knocking a cross into the net.
"Proud to score on my debut," Bale said in a tweet, adding "just disappointed not to get the result. Looking forward to Tuesday now."
Madrid has lost in the semifinals of the lucrative competition in the last three seasons, last season to Borussia Dortmund.
"Real Madrid have not made it into the final of the Champions League since 2002 and that's amazing when you think about it," Ancelotti said. "I think it's been too long for a club of Madrid's stature."
In the other group match, FC Copenhagen will host Juventus.