Alonso started the first grand prix of the season from fifth position but ended up fighting for victory after his Ferrari performed strongly in race trim.
The Spaniard was unable to match Kimi Raikkonen's pace in the second part of the race, the Finn winning by over 12 seconds having pulled off a two-stop strategy, unique among the leaders.
Alonso conceded the Finn was simply too strong in Melbourne.
"It was a fantastic, fantastic race, fighting all through the race," said Alonso. "The race was action every lap and I personally enjoyed it, obviously.
"At the end it was a little bit sad not to be able to win the race, but Kimi was fantastic today, the Lotus as well. We have to congratulate them for a fantastic race."
The Ferrari driver, on a three-stop strategy, admitted that Raikkonen's ability to stop just twice was a concern ahead of next week's Malaysian Grand Prix.
"It is a worry, yes," he said. "Lotus did a very good job and Kimi was driving fantastically and could do two stops. So we have to analyse it. We have only four days to the next race and we have tough opponents.
"But at the end I am extremely happy. We had an extremely difficult start to the season two years ago and last year and this year is very different. We are very optimistic and have an interesting season ahead."
Team-mate Felipe Massa completed a promising start to the season for Ferrari by grabbing fourth position.
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