The 2007 world champion has scored two podiums over the season, leaving him fifth in the standings heading into the season finale - while Vettel is two places and more than 100 points ahead in the standings, with three victories and 13 podiums in total under his belt.
Asked for a verdict on his 2015 campaign, Raikkonen replied: "Pretty average, I must say. Better than last year but still far away from what it should be. But that is life and next year we try again."
Raikkonen said there is also room from improvement from Ferrari, pointing as evidence to his record of five retirements - and the fact his best result of second in Bahrain was not necessarily his strongest race.
"The end result was probably best but it doesn't meant that we are somehow better than other weekends," Raikkonen said of Bahrain. "The end result, it just looks good.
"We improved a lot from last year but we're still not happy and when I don't finish five races it's quite a big… many races out of how many we've done this year. You don't expect to be very high up and fighting for a lot.
"So we have to improve - and I'm sure we can still improve it. Next year is a new challenge; I'm sure we can do better."
WATCH: Kimi Raikkonen on Ferrari's prospects for 2016
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