Here are my thoughts on the guys right now, having not looked at each (other than Parker) very closely:
1) Embiid - guy who hasn't played much basketball and who has a bad back. A bad....back.... Larry Johnson was one of the most explosive inside scorers ever - got a bad back, couldn't lift off at all. Steve Nash - bad back, done as a star. Larry Bird - same. Grant Hill and Ilgauskas had like 1,000 foot surgeries. Each was able to eventually become an all-star again. But when you get a bad back as an NBA player, you are 45% of the player you once were, forever.
God bless the guy, maybe he just had a low pain threshold and really wasn't that hurt - but I will take him at his word. He hurt his back so badly that he couldn't play in the NCAA tourney. I am not drafting him until 7-8-9 range.
2) Wiggins - look, I don't care for the fact that his dad is Mitchell Wiggins who was suspended for cocaine usage and wasn't that great of a player anyway. But Kobe is Joe Bryant's son, so let's move on. I would pick Wiggins #1. He is 6'8" without shoes. He has a ridiculous vertical, is extremely explosive and has scored 40+ points in a college game. If he is willing to work AT ALL he should be an all-star caliber player who can guard three positions. Michael Beasley is a horrible drug man who tries almost not at all and he has had decent NBA years despite no ballhandling ability and no understanding of offensive or defensive concepts. So to say Wiggins cannot be an all-star level player is to ignore his remarkable athleticism and the fact that he has shown no signs of being a dog.
Wiggins' primary drawback is that he came into college with the tag "the next LeBron" - good lord, come on. I saw both guys play in high school games. LeBron was like something I had never witnessed before. Wiggins was, well, just very good. But that is not the kid's fault. Name an athletic player who when they came into the league had a great jump shot? Maybe Ray Allen? But if you gear it up to the top level guys - MJ, Kobe, Wade, LeBron, McGrady, Vince - none could be counted on to make an open jumper early on, and they never tried, they just barreled to the hoop. They eventually learned to shoot. And if you are almost 6'10" in shoes and have learned to shoot, you are gonna be a bitch to guard.
3) Jabari Parker -- As a Duke fan, I saw Parker play the most. If you are a fan, you say, "Charles Barkley". High rebound rate, great on the break, undersized, but can jump and can get steals and run the break. If you are not a fan, you say, "Derrick Williams" - chunky, not particularly explosive in traffic, doesn't understand defensive concepts or try very hard to improve. Throws himself out of control off the dribble and does things that great players just don't do.
If you asked me whether I would take Parker or Aaron Gordon, I take Aaron Gordon. Parker will play only one end of the court and that will be your return on investment. If he is Barkley, then you have won. If he is Derrick Williams, then he is a bust or maybe a guy like Al Harrington who runs through the league for 13 years trying to convince people he is good.
4) Julius Randle -- I like Julius Randle. I shouldn't, because he is an undersized 4 who is left handed, but let me tell you why I like him. He plays to win, plays on the offensive end at a high rate of speed, and firmly believes that he is really, really good. He shares these attributes with............Kevin Love. His weaknesses - poor defensive effort (Love), poor steals+blocks (Love), cannot dribble more than once or twice (Love) and won't pass to teammates (Love before this year). He measured in at 6'7 3/4 inches without shoes and at 255 pounds - both identical to Love. So there is absolutely no reason that Randle cannot be a 10+ rebound guy who can hit an open shot and draw fouls underneath.
Is he going to take your shitty 15 win team to 45 wins? No. He is not Bird/LeBron, OK. But in 2-3-4 years could he be the best guy on a low-level playoff team? Yes. Could he be a really, really good piece for a title team? Yes. I enjoy the chatter of the scouts about "he is no Zach Randolph". When Zach left Michigan State he wasn't highly regarded at all. That held true off and on up to when he went to Memphis (they got him for basically nothing in a salary dump). He just works harder than everyone and has developed a difficult offensive game to stop. Is Zach Randolph obviously a better talent than Julius Randle? Absolutely not.
He is said to be slipping - some lucky club will grab him where they get him. He will be a very good NBA player.