I'm not sure anyone in Candide was ever really happy, including Candide. Perhaps the folks in El Dorado, it could be argued, are happy, but happiness seems to only be potentially achievable in the face of unhappiness, something that the denizens of El Dorado have not, seemingly, faced in their isolation.
Voltaire's satire remains critical of those who look for happiness at the expense of everyone else's. This includes war, greed, knowledge, philosophy, politics, and religion. This quest finds the characters, including Candide, searching for that elusive thing that they feel will bring them happiness.
The closest Candide gets is at the story's close. He got what he wanted (a now wretched Cunégonde), but, ironically, she is now not so desirable. What do you do then? Candide answers: "we must cultivate our gardens." In this commune, everyone has a job, a purpose to keep them busy and away from boredom, vice, and poverty. And even though Pangloss — in spite of the tortures he has endured — still waxes optimistically, Candide is no longer fooled.
On a final note: it could also be argued that, like the folks in El Dorado, Candide was happy at the beginning in the castle of the Baron of Thunder-Ten-Tronckh, but like childhood naïveté, that castle is soon obliterated by the war of the everyday. This youthful, cloistered life must come to an end. In order to find happiness, Voltaire seems to suggest, one must first experience the other pole.
Yes, I think Candide was happy at the end: that was the whole point of the garden. I have the last line of Candide taped to my monitor: "Cela est bien dit, répondit Candide, mais il faut cultiver notre jardin."
It's essentially Buddhist, I think: life is suffering, suffering is caused by desire. Stop desiring and talking idle chatter and just live, simply.
I agree with grlucas, that Candide is no longer fooled by Pangloss and that's a big achievement. About Cunégonde -- her change is no different than anyone's in aging, in its effects for Candide, after all: she is now old and homely relative to her youthful beauty: but she has become a very good cook! And there's a lot to be said for that.
"like childhood naïveté, that castle is soon obliterated by the war of the everyday. This youthful, cloistered life must come to an end." This, I agree with, and the phrase "the war of the everyday," as Candide might say, "est bien dit."
"In order to find happiness, Voltaire seems to suggest, one must first experience the other pole." But this statement I would take issue with. Voltaire certainly shows the other pole entirely, with grotesque sufferings. But Pangloss NEVER learns from this what Candide does, so the other pole is not sufficient. I'd say "the war of the everyday" is quite enough to force anyone to search for life's solution without experiencing the famous sufferings of our party in Candide.