It's a bit of a shame to see teams from the same national leagues competing against each other that early on, maybe it would be good if the drawing rules were changed to prevent that from happening. We have two such situations: Real Madrid Vs Atletico Madrid and Bayern Munich Vs Bayer Leverkusen.
The outright odds for the UCL winner, updated for the results of the draw, are as follows:

I think it's fair for Real to be at the top, but I don't think betting on them is a good move, I rather put my money on a team with a higher payout. A potential dark horse would be Atletico, if they manage to get past Real, the hardest part would be done. In the last 5 head to head games between Atletico and Real, we had one win each and 3 draws, so looks pretty even. So if we assume both teams are on a similar level, the odds of x21.0 for Atletico sound really attractive, especially compared to only x4.30 for Real.