Bayern have the third most champions league trophies and the most quarterfinal’s in the tournament oat. The one thing that’s underrated about Bayern imo is their consistency. Bayern are almost always better than Barca and ac Milan (other second best contenders) and are always ucl favourites due to their yearly performances. Their fan base is the one of the largest in the world (+ the club with the most members), they have legends in every position (some in contention of best in their position I.e Neuer), the culture, the atmosphere.
I may be biased as a Bayern fan however I believe Bayern > Barca and AC Milan
Barcelona had a massive bump due to Messi. It remains to be seen whether they can regain that same stature.
Barcelona had a massive bump due to Negreira. It remains to be seen wether they can retain the adulterated titles they won.