They competed bravely against the leaders but the game was effectively lost when they had a player sent off five minutes before half-time.
They never gave up and matched Guernsey up front but the backs were over stretched with a man short and three second-half tries gave the Islanders a bonus-point victory.
Guernsey and Old Elthamians, who have shown extra strength, will now race for the title.
But Chichester have enjoyed another good season and will finish third or fourth.
Gs kicked off and attacked and although Chichester covered well they did not release quick enough and Barton kicked a penalty for the visitors. Chichester attacked and a Sevi Sevuia run promised something but another penalty gave Gs the clearance.
The Blues went again and Pearham slotted a penalty.
The Chi backs ran hard from midfield and a Billy Toone tap penalty made ground but was ruined at second phase for not releasing.
Scott Barlow made the first of his strong carries and Stuart Pearham found touch with an excellent kick. Promising positions came twice more but the referee found fault with the rucking.
Gs won yet another penalty, followed by a lineout. A long throw to the back was palmed to fly-half Campbell, who came at pace on a deceptive line to score near the posts. There was a suggestion of crossing to block a possible tackle. Barton added the extras.
Gs missed a penalty for offside and Ski Sauliga went over from a lineout at the other end but had put his foot in touch. Richard Adams,Toone and Sevuia combined before Adams met a hard tackle.
Ben Polhill seized a loose ball and kicked on but it was just too long. Chichester drove and rucked down the left despite fast and big tackles by Gs’ impressive back row.
Pearham sent a penalty into Vultures’ Corner and the large crowd roared them on. They rucked five metres out as Gs resisted and things became heated as a Gs defender seemed to be killing it on the ground.
The Blues’ loose-head prop Ash Wheeler made the fatal mistake of using his boot and was dismissed. Instead of a yellow card for Gs and a possible score, Blues were down to 14 men for the rest of the game.
Nick Shopland joined the front row and Manoa Satala in the centre was sacrificed. It was sad as Chichester were getting on top despite a bad penalty count against them.
Adams beat two men and passed to Richard Deed, whose accurate kick forced Gs to carry over their line.
Quick scrum ball saw the Chi backs go across field twice with secure handling but fail to breach the Gs massed drift defence. It was 10-3 to Gs at the break.
Chichester attacked from the restart but knocked on. Campbell counter-attacked and Ben Polhill rescued with a vital tackle. Gs upped it and Toone made a try-saving tackle before they pressed hard to the right.
They missed a penalty at a lineout but following a disappointing Chi drop-out, their very fast backs were forced out near the corner. The ball was caught at the lineout and delivered to Campbell who slipped a close pass to inside centre Batiste at pace to run in their second try. The conversion was slotted by Barton.
Andy Gray entered the fray as back-row replacement and made his presence felt.
Chi advanced but Seviua put his foot in touch and another attempt to penetrate finished with a knock-on 15 metres out.
Gs constantly threatened with counter-attacks and Ben Polhill was once again fast enough to stop another break.
It was no surprise when they won their lineout at the corner, rucked and transferred to scrum-half Barnes to cut around blindside and score near the left corner.
The Blues threw themselves into the physical battle. Adams and Toone rampaged forward before a heavy tackle into touch resulted in an exchange of handbags.
Back came Gs and Batiste’s long touch kick produced a flowing move with inevitable overlap for a score in the corner by the outside centre on the gallop.
Toby Golds was brought on wide and showed immediate aggression on his fresh legs.
Chichester spent the last few minutes hammering the Gs line and a dart-through by Pearham almost succeeded.
The Blues finished in style with Tom Polhill and Golds breaking first tackles and Gs looking tired and Campbell hobbling.
Golds grabbed the consolation try when he broke free from a half-tackle and plunged over. Pearham converted to make it 27-10 to Gs, which rather flattered them.
Certainly it would have been interesting to have seen a second half with a full complement.
Director of rugby Paul Colley said: “It was a hard game and I thought we played well. You can’t expect to beat a leading team one man down.
“The referee should have blown for a Chi penalty or penalty try when the ball was killed and he had already played advantage to us for a previous infringement as we drove to their line.
“This caused irritation in the red zone but I accept he had no option to dismiss under the laws.
“We put Guernsey under a lot of pressure and showed great commitment.”
This week the Blues are away to Haywards Heath (3pm).
CHICHESTER: Wheeler, Lawrence, Veltom, Barlow, Blount, Sauliga, B Polhill, Kasujja, Toone, Pearham, Sevuia, T Polhill, Satala, Deed, Adams, Shopland, Gray, Golds.