It's very hard to pick only one and it's always going to be difficult to quantify talent and weigh that above favouritism - the appreciation of music is always fairly subjective (which makes it weird that within a genre there's often so much agreement on who's best).
Back in the day I'd have said Posford without question. Hallucinogen was pretty much my introduction to psytrance (I know some classify it as Goa trance. Really his work almost made its own genre).
More recently I too have been highly impressed with the works of Christer Borge-Lunde (RA, Dimension 5, etc.) and he just seems to get better and better. Shift from Unearthly is now one of my all-time favorite tracks - exquisitely layered with an amazing memorable melody and barking 303 notes.
For the most talented recent artist I have to mention Rita Raga. She's also hugely underrated. Her Mystic Melodies album is a lovely mixture of mellow downtempo and intense fullon remixes. She sings beautifully on her tracks often with deeply inspiring lyrics and she plays multiple instruments as well.
