He was utterly above all genin at the time. He also made easy work out of sound ninja.
The k11 at the time defeated Orochimarus CM 4, so I say he's stronger than them also.
He also defeated a dying Kimimaro. Clearly he was the strongest guy of his age group by far (13-19~)
However, guy swatted his sand away with one swipe of his hand... Something no one has done.
I place him around high chunin- low jonin since Guy is about Mid-Kage - Low Demi-God depending upon his gates.
Part 1 Gaara is high Chunin in base, Jounin with his mini Shukaku transformation, and Kage in full Shukaku mode. Gaara was weaker in the preliminaries than when he shows up in the retrieve Sasuke arc and that's a Jounin blocking a mid Chunin level ninja attack. Gai's base is Jounin level, with the gates up to 7, he's Kage level and 8th gate above Kage but not Demi God. The fact that Gai had to go 5th and 6th gate to a Kisame clone that had about 7.5% his reserve and 7th gate against a weakened Kisame who doesn't have Samehada. Gai in 8th Gate is below EMS Madara level who can beat him.