The 67-year-old has taken the reins at a club residing bottom of Serie A, with the Blucerchiati posting just three points from their opening seven games to cost Eusebio Di Francesco his job.
Fulham was also rooted to the foot of the Premier League table when the Italian took charge in November 2018, but he was dismissed after winning only three of his 17 games at the helm.
However, Ranieri considers the task at the Stadio Luigi Ferraris to be vastly different from the one he took on at Craven Cottage.
"Sampdoria are not Fulham. Don't forget, Fulham were a newly promoted club with players who had never been in the Premier League," he said.
"In the January transfer window, they followed the advice of algorithms. This is totally different. Sampdoria have played good football and are struggling, so now need the desire to fight hard.
"The quality towards the lower half of the table has improved significantly, which adds difficulties to us, but is also a sign that Italian football is returning to the top level."
It is Ranieri's birthday on Sunday and he will mark the occasion with a home match against his former employers and the club he supports, Roma.
"I am a Roma supporter, but have always appreciated Samp," he said, having also succeeded Di Francesco at Stadio Olimpico.
"I was happy when they won the Scudetto [in 1991] and disappointed during the European Cup Final defeat at Wembley [in 1992]. I respect Di Francesco and hope he finds a new role as soon as possible.
"As for facing Roma on my debut – and my birthday – it's all wonderful. Naturally, when we step on to that pitch, there is no love, but only professionalism. May the best team win, we will try to give our best."