I will define myself as a college basketball expert, relative at least to a Celtics message board -- I didn't really start watching NBA ball with regularity until 2005, but watched as much NCAA as I could get my hands on for a decade before, and still only watch the C's when I watch the NBA.
Parker is as impressive as any freshman small forward I remember seeing at a major college program since Carmelo Anthony. He might be better, might be worse, because a decade can do a lot to your memory, but he should be in the same discussion as Melo. Here is a side-by-side comparison of their stats, for those who like statistics.
http://statsheet.com/mcb/players/compare?add=carmelo-anthony&i=1&p1=jabari-parker(Note: I'd put Kevin Durant above Melo, but I also think they weren't playing the same position. Durant was unquestionably a stretch 4, and sometimes a stretch 5 in college, whereas Melo and Parker are playing a much more similar position. If you want to argue that I should compare Parker and Durant, I will tell you KD was better.)
I've said in other posts how much I like Embiid. I do think college centers are harder to judge, especially elite ones, because they so rarely have anyone near their level to go up against. Also, they sometimes rely very much on having a decent pg to get much going offensively, since 7-foot tall 19 year-olds (and heck, 22 year-olds), rarely have much in the way of offensive refinement (because they never need to develop it in college or high school to get their shot off). That said, Embiid is definitely a defensive difference-maker, and a decent passer out of the post when double-teamed. He's better than Roy Hibbert as a freshman, although certainly not Roy Hibbert as a senior. Greg Oden, in my opinion, was better as a freshman, which a) makes me sad about what his career has amounted to, and b) remind you there is no sure thing. Due to the scarcity of elite centers in the world, Embiid is my #1 hope for the C's to draft. That said, he only plays about 50% of his team's minutes so far, and is someone who's I think would really benefit from a second year in school, because he is new to the game. For personal monetary reasons, I think he should come out, but from a basketball perspective, Embiid after 1-2 more years of Bill Self could be on a hall-of-fame track. Here's a comparison of Embiid, freshman Hibbert, and Oden.
http://statsheet.com/mcb/players/compare?add=greg-oden&i=1&p1=joel-embiid&p2=roy-hibbert&roy-hibbert=2004-2005I think Wiggins is getting to the point of being underrated at this point. He hasn't looked as consistently good as Jabari Parker, but there's no question in my mind why everyone was fawning over him prior to the start of the year. I think the expectations of him had been set at MVP-LeBron level, which was very unfair. To me he and Parker are still the clear top 2 in the class, and if they go 1-2, there will be two happy teams at the top.
I think Randle has at times been dominant, but I think any talk of him being selected above Parker or Wiggins this point isn't based on evidence. Randle punishes the mismatches he gets in the paint, which is frequent, but doesn't have 3-point range, and can get very careless with the ball. He looks like a very good college freshman power forward, but much more like an Anthony Bennett or Derrick Favors (very very good), than like a Chris Webber whom you remember for decades.
I like Marcus Smart a lot more than other people here, I think. He's probably the best player at a major college of taking over a game this year. Last year that player to me was Trey Burke. OSU has other talent, but he is the transcendent player that makes that team go. I'd probably take Smart above Randle if I were starting a team.
I haven't seen enough of Gordon in Arizona, because I don't stay up as late as I used to watching West Coast basketball. (Getting older stinks). What I have seen however, has been very good. Looking at his game log lets me know that I've missed his stinkers, and why people have gotten down on him. His best games have definitely made him look like he's in the same class as Randle, and his worst games as someone who slides out of the draft.
My feeling is the top 5 draftable players in college are Parker in Wiggins in your top 2, and Smart, Embiid, and Randle as 3-5. To me, this is a deep top 5. I think many years, a player of Embiid's quality or Smart's quality goes #1, and someone like Randle is consistently in the top 3 in all but the deepest years. With Exum also being in the mix, one of those guys will likely slide out of the top 5, which to me means at #6 you're getting someone who in most years would be no worse than #3.
To me this draft will have the best player since Kevin Durant, and also the best top 2 since that draft as well. While I'd take the top 2 of 2007-2008 over the top 2 this year (again, this is without prior knowledge of the sad case of Greg Oden), I'd probably take anyone in this year's top 6 over Al Horford, who went #3 and has been a very good NBA player. Jeff Green went #5 that year, and I see Glenn Robinson III as a very similar player, and it looks like he'll be in the 10-20 range. To me there is no panic if we miss out on one of even the top 4 picks. This draft is rightfully seen as historic at the top of the class. The depth of it also potentially extends very far through the first round, depending who comes out earlier.
One final note for newer college basketball watchers -- I think the conference schedule, which is just starting, tends to be a better barometer for performance than the non-conference schedule, especially for freshman (at major colleges). In the non-conference schedule, you see guys going up against lesser competition most nights. Sure, there are the big games (and there has been better scheduling of those big games over the past decade), but most nights it's against some small-conference school who won't stand a chance of beating you. There's less scouting of players, and more "weird" systems run, so that can have a pretty big impact, positively or negatively, for players. Once you get to the conference schedule, there's more film on the players, and opposing team's are much more familiar with each other. Dominating conference play is much more important than early-season or tournament play, in my opinion.