Newcastle, second from bottom, were undone by a spectacular overhead kick from Japanese forward Shinji Okazaki in the 25th minute, leaving them deep in relegation trouble with nine matches remaining this season.
Benitez, who replaced the sacked Steve McClaren last week, said he was encouraged by the way Newcastle took the game to Leicester early on.
"There were a lot of positives. We did well, you could see the commitment and the passion," Benitez told Sky Sports television.
"The team showed they are convinced they can win. We cannot change this result but we can be happy in terms of the commitment of the players.
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"We started really well and had two good chances," the Spaniard added. "After 20 minutes Leicester started pushing and they scored and then played the game they like to play, on the counter attack.
"Leicester work really hard, they are pushing and their (high) tempo is not easy for any team."
Benitez, who was sacked by Real Madrid in January, will now turn his attention to Sunday's relegation crunch match at home to fourth from bottom Sunderland, Newcastle's bitter north-east rivals.
"Our game against Sunderland is a derby and it will be important for everyone," said the former Liverpool, Chelsea, Valencia and Napoli manager.
"But I have a feeling the fans are really good and they are our number 12 for the next game."
(Writing by Tony Jimenez; Editing by Peter Rutherford)
