It depends on how you define success.

I suggest you read what /u/anthropology_nerd has to say in the Myths of Conquest Series over at /r/badhistory. The first entry would be of particular interest, as would Part Three and Part Five.

All of the other sections are listed in Part Nine, the finale

EDIT: See also what /u/drylaw has written about whether the conquistadores could see indigenous societies as equals or superiors.. There's also a response about suppressing indigenous culture and memory in centuries to come.

/u/Snapshot52 has written about whether Indians were ever the aggressors in colonial conflicts, or purely defensive., again a very broad question.