Rayman Origins' was indeed initially a prequel, but that was dropped by the time it was released. Rayman's creation is elaborated upon, but it's pretty clear it's a past incident. Given also the fact that the Magician clearly betrays Rayman, turns evil, and then splits into the five dark Teensies. And also the fact that Polokus/Bubble Dreamer is awake, the UbiArt games have to take place after Rayman 1 and 2 at the earliest.
Rayman 3 doesn't directly call back to R1 and R2 in its plot, but Globox does call back to Rayman 2 with one of his fourth wall jokes, and the 2D Madness game clearly notes how Rayman 1 took place when " Rayman remembers being a kid, when everything was in 2D."