"These are the generations of Noah...[Noah was a righteous man, perfect in his generation]. Rabbi Yochanan said: "In his generation" he was considered righteous, but not in other generations. Reish Lakish said, "In his generation" and even the more so in other generations.
(ב) בדרתיו. יש מרבותינו דורשים אותו לשבח, כל שכן שאלו היה בדור צדיקים היה צדיק יותר, ויש שדורשים אותו לגנאי, לפי דורו היה צדיק, ואלו היה בדורו של אברהם לא היה נחשב לכלום:
(2) "In his generation..." - (Sanhedrin 109) Some of our rabbis interpret this as praise, meaning, all the more so, if he had been in a generation filled with righteous people, he would have been even more righteous. And there are those who interpret it as criticism, meaning, if he had been in Abraham's generation, he would not have been thought of as anything special.