Brendan Rodgers' side looked set to complete a stunning march to the title after beating City 3-2 on April 13.
That win put Liverpool's fate in their own hands, despite City having two games in hand, but a fortnight later their hopes were dashed by a 2-0 home defeat to Chelsea.
Steven Gerrard's slip allowed Demba Ba to open the scoring as Jose Mourinho's side frustrated Liverpool for large parts of that Anfield clash.
That allowed City to steal in, winning their last five games to move ahead and seal a second title in three years, which Pellegrini believes was the right outcome.
Speaking ahead of City's clash with Liverpool on Monday, he said: "Of course, Gerrard was unlucky in that game, but Liverpool were not unlucky to miss out.
"When they beat us 3-2 at Anfield and people said they would go on to win the league, I thought we were very unlucky to lose.
"Liverpool might have been unlucky against Chelsea but they were lucky to win against us.
"Though we lost at Anfield we never felt the other team was better than us, or deserved to win the title.
"We felt we should have won the game and it just made us more determined to win the rest."
Manchester City have once again spent lavishly on their squad in pre-season, signing Eliaquim Mangala, Fernando and Willy Caballero among others.
But Pellegrini insists his achievements are not lessened by the cash available to spend.
"People think it's just about money but it's not," he added. "You need a strong squad if you are going to challenge for the title, and that costs money, but other teams have spent more than us and still not won.
"You still have to sign the right players, you still have to perform as a team.
"We have strengthened our squad a little over the summer and I am happy with it."