I would say it doesn't get any bigger than Champions League and World Cup and I think I am being objective here. Well, unless people give more importance today to things such as head to head records between Real Madrid and Barcelona in the 50s rather than European Cup trophies. In that case I would have to agree with you. But I doubt many people in this forum are aware of that head to head stat.
If we rate defenders based on records vs certain teams at their peaks, (and I say this because Barcelona have been in pretty good shape for most of past seasons since Ramos is a professional footballer), I think nobody is going to look particularly well at the end of the day. Did Manchester with Rio do particularly well stats-wise when Barcelona was in good shape? Well, 3-1 and 2-0 defeats suggest that's not the case.
Now, the question is, has Ramos been good in big games overall in his professional career? Absolutely not. He's been magnificent. I mean if we really made an effort to show every big game with Ramos being stellar we would really be flooding this thread, and users like
@adexkola would increment his hate towards him even more. And I don't think that's necessary at this point in time