Interesting thread, so I'll add to it. For those unfamiliar with "Win Shares" it's a metric designed to allocate a portion of each win to an individual. It's similar to WAR in baseball as it's a stat that accumulates over time, so the more minutes someone plays, the higher their WS's will be. Therefore it's usually combined with "Win Shares per 48" to give a full picture of a players value. Win Shares is a good metric because, unlike some others, it encompasses defense as well as offense. WS is actually the sum of OWS and DWS. If anyone is bored and wants to read about it here's a better explanation.
https://www.basketball-reference.com/about/ws.html
I went through every season back to the 95/96 season (as far back as WS's are recorded). Here's a list of players that had an individual season with a Win Share total above 5.0. I included a couple just below of note.
1. Antonio Gates 01/02 - WS 6.5; WS/48 0.223
2. Haminn Quaintance 07/08 - WS 6.4; WS/48 0.306
3. Jimmy Hall 16/17 - WS 6.0; WS/48 0.206
4. John Edwards 03/04 - WS 5.7; WS/48 0.296
5. Mike Scott 07/08 - WS 5.7; WS/48 0.197
6. Chris Evans 12/13 - WS 5.5; WS/48 0.192
7. Trevor Huffman 01/02 - WS 5.5; WS/48 0.181
8. John Whorton 99/00 - WS 5.3; WS/48 na.
9. Trevor Huffman 00/01 - WS 5.0; WS/48 na.
10. John Whorton 98/99 - WS 5.0; WS/48 na.
11. Justin Greene 09/10 - WS 4.9; WS/48 0.206
12. Haminn Quaintance 07/08 - WS 4.8; WS/48 0.306
13. Andrew Mitchell 01/02 - WS 4.7; WS/48 0.157
One limitation of trying to use Win Shares for this type of thing is if a player never plays on a good team, he will likely never have a good chance at a WS near 5.0 in a season. However, the counter argument would be, if a player never played on a good team does he belong on the all time starting 5? Garbage time stats are a real thing.
So based on this list I would say there are 4 That are locks.
Gates, Q, Edwards, and Huffman.
I honestly believe Q might have been the best all around player we've had in the 17 years I've been watching. So the question who would be the 5th comes down to are you actually trying to build a starting 5 or just pick the 5 best players. If you're trying to build a starting 5 I think the 5th is either Mitchell or a prolific shooter like Manley to stretch the floor. Or possibly Evans but that might be a stretch playing at guard. I've always felt Evans was one of the most underappreciated players we've had. Now, if you're just saying give me the top 5 players overall regardless of position then my 5th would be Hall. Don't forget, if Hall didn't get mono as a Sophomore he could've made a serious run at the all time scoring record despite only playing 3 seasons here.
As for players before this era, I'll defer to those who saw them play.