Ramires and Eden Hazard gave the Blues a 2-0 lead which Shaun Maloney halved after 58 minutes before Lampard's 86th-minute strike saw him move to within four of Bobby Tambling's club goalscoring record of 202.
Substitute Marko Marin added a stoppage-time fourth as Chelsea, who had won just three of the previous 10 games, triumphed for the first time since the defeat of Arsenal.
"We deserved to win," Benitez said. "To win is something you have to do. Top sides, if you want to win something, you have to be consistent winning. It's normal.
"But it's not the end of the world if you draw a game you deserve to win.
"The problem for me would be if we don't create chances; we create chances every game. We score goals. We're making some mistakes, but we have a lot of positives. Four goals could be six goals at the end."
Benitez has finally accumulated more Premier League points than his predecessor, Roberto Di Matteo, whom he replaced in November - albeit in two more games.
It is a result which is likely to at least delay Chelsea owner Roman Abramovich, who is not renowned for his patience, reaching for the trigger. Benitez was unfazed.
"It was just speculation," he said. "Nobody is in contact with the owner to find out if he says this or that.
"It is my job: try to win every game. That's it, so I have to concentrate on that."