Well I hardly think Parker would have been chosen over Griner when Parker was a freshman. Just because Geno said Parker does things no one else can doesn't mean she's better than Griner. Dee is widely acknowledged as the best player in the world. But Stewie and Brit and Candace can all do things Dee can't. Brit can do things Parker can't. And Stewie as a freshman is better than Parker was as a freshman.
Don't think you can make a strong argument outside of the NCAA tournament that Stewart was better as a frosh than Parker. Parker was much more consistent as a freshman, carried Tennessee offensively while having to play out of position for chunks of the season due to injuries. Every opposing defense game planned to stop Parker, and no one could. Look at her production against the best opponents UT faced in 2006:
Maryland-19 points, 8 rebounds
Stanford-21 points, 12 rebounds
Connecticut-13 points
Georgia-26 points, 10 rebounds, 5 assists
Duke-17 points, 5 rebounds, 5 assists, 3 blocks, 2 steals
LSU-23 points, 9 rebounds, 3 blocks
Georgia-19 points, 14 rebounds, 5 blocks
Georgia-26 points, 12 rebounds, 3 assists
LSU-20 points, 6 rebounds, 3 assists
Then in the tournament she averaged 22.5 points, 6 boards, 3 assists and 3.8 blocks while playing out of position. She was the most talented player in the country the minute she stepped onto the court. She was so fluid and polished as a post player, was a great passer, ball handler, shot blocker, overall athlete. Had she been available for the 2006 WNBA draft she would've been selected 1st overall over Augustus.
Stewart has an incredibly high ceiling and played phenomenally in the tournament, but she was nowhere close to being as consistent as Parker was as a freshman, nor was she as polished as Parker. She also had the benefit of playing alongside an All-American center and an All-American wing in KML which means defenses never built game plans around stopping Stewart, usually it was KML who was the focus of the defense. I definitely think her ceiling is off the charts with her skill set and physical attributes, and I do think she'll be the next great one ala Parker/Moore of recent years, but Parker was definitely further along/better as a frosh than Stewart.
Back to the original post, Griner would definitely be selected first overall, she probably would have been selected first overall over Charles in 2010, maybe Moore in 2011, and 1st in 2012 over Ogwumike. Women's basketball has never seen a physical specimen like Griner, and as good as she is now, she still has great upside. After her, I would take Stewart #2 based on potential. Based on immediate impact in the WNBA, I'd take EDD at 2.