Keane reached his century in stoppage-time at White Hart Lane when he latched onto Radek Cerny's clearance and squirmed a shot under Craig Gordon.
"I think it's a great achievement for him, the club and the Spurs family," said head coach Ramos.
Keane has scored 16 goals this season for Spurs and fired 15 in 15 appearances at the back end of last season, marking an incredible year for the Republic of Ireland striker.
Aaron Lennon had opened the scoring in the second minute when he prodded past Gordon from Jamie O'Hara's cross from the left flank.
Defoe, who has been linked with a move to Aston Villa, was named captain for the day as Ledley King was rested, Paul Robinson is not in favour and Keane started on the bench.
"The first three captains were out of the first XI and I needed an alternative," said Ramos. "I had to choose somebody."
Berbatov also hit the crossbar and Jermaine Jenas went just wide when he raced through, but Spurs were nearly made to rue their misses as Sunderland began to threaten towards the end of the first half.
Paul McShane had a header cleared off the line just before the break and Spurs had to withstand plenty of Sunderland pressure in the second half.
Daryl Murphy curled a shot wide, Kenwyne Jones had a strike disallowed for offside and Cerny saved superbly from Michael Chopra and Liam Miller.
Ramos praised Cerny, adding: "The more he has played the better his form has been. He had a great match."
Sunderland boss Roy Keane said: "If you give two goals away like we did you don't deserve to win any football match.
"You can dress it up all you want.
"Their goalkeeper obviously made some outstanding saves, credit to him, but if you concede a goal after 111 seconds it's not ideal with our away record.
"The game is 90 minutes, you're not going to dominate any game from start to finish but you have to start well. Every manager wants a decent start and at the top level it is about concentration. That wins and loses football matches."