Lampard's 200th Chelsea goal and Eden Hazard's second-half strike saw last season's Champions League winners leapfrog Tottenham and move within four points of second-placed Manchester City.
Both Spurs and City lost at the weekend and Rafael Benitez's side will have their three remaining targets firmly in their sights when the season resumes following the international break.
"We are in good form and everyone is at it," Lampard told the BBC.
"There is a good feeling around the place and we need to carry it on until the end of the season.
"It is one of my best days. Obviously, winning the Champions League and championships are the best, but personally getting 200 goals for the club, I never thought I would touch that so I am pleased to get it.
"Everyone keeps talking about the goalscoring record, I would rather people kept quiet.
"The important thing is trying to score goals to win games."
Chelsea dominated against the Hammers, as they carried on the momentum from the second half of the FA Cup quarter-final with Manchester United, which they drew to force a replay on Easter Monday, and the Europa League defeat of Steaua Bucharest.
"The good thing is we have had three very good games, but the bad thing is we have the international break now," Benitez said.
"Hopefully, mentally, they will relax, they will change their environment and they will come back with a fresh mind and fresh legs."
West Ham, who inflicted Benitez's first defeat as Chelsea boss in December, were second best throughout, but had chances.
Meanwhile, the Metropolitan Police are investigating after missiles were hurled from the away end in the direction of Chelsea's players as they celebrated Lampard's goal.
The incident could lead the Football Association to take disciplinary action.
CCTV footage will be studied to identify the offenders.