Most are good, some are great, a few are terrible.
2012 - Nail Yakupov - Edmonton Oilers: To be fair to Edmonton, about 99% of the picks in the 2012 draft were mistakes. The Oilers picking Yakupov were one of those 99. The best players in the draft were goalies Andrei Vasilevsky and Connor Hellebuyck, but besides those two, it was pretty bare. Yakupov ended up playing just six seasons in the NHL before leaving for the KHL. He had 136 career points.
2000 - Rick DiPietro - New York Islanders: The 2000 draft did not produce many great NHLers, but DiPietro going first overall is ridiculous. DiPietro was a starting NHL goalie for just four years. Turns out, the best player in the draft was taken 205th overall though, his name is Henrik Lundqvist.
2006 - Erik Johnson - St. Luis Blues: I think it's pretty easy to say that this one was a mistake. Guys like Jonathan Toews, Nicklas Backstrom, Claude Giroux, and Nick Foligno would follow Johnson in the first round. The Blues gave up on him after three years anyway, and he has since spent a decent career with the Colorado Avalanche.
2017 - Nico Hischier - New Jersey Devils: Although it has taken a few first overall picks a few NHL years to develop (Nathan MacKinnon, Taylor Hall), at this point, it seems like Hischier might be a bit of a disappointment. The Devils might regret thrusting him into a huge role so early in his career.
2011 - Ryan Nugent-Hopkins - Edmonton Oilers: Shockingly, Nikita Kucherov was drafted late in the second round of the 2011 draft, so you can't blame just Edmonton for missing on him. Although Nugent-Hopkins is a good player, he is not worth a first overall pick. Edmonton, if not Kucherov, should have gone for Gabriel Landeskog or Mark Scheifele who went second and seventh respectively.
2014 - Aaron Ekblad - Florida Panthers: Kudos to Florida for having the guts to take the first defenseman first overall since the bust that Erik Johnson was. The 2014 Draft had a lot of depth, the biggest star coming late in the first round in David Pastrnak. Ekblad has turned into a solid defenseman with a little offensive flair, but he was not worth a first overall pick.
2018 - Rasmus Dahlin - Buffalo Sabres: At this point in time, it's absolutely impossible to tell how good Dahlin will end up being. Most elite defenseman take a few years to blossom. We do know that Dahlin has great skill though, so the future is bright.
2001 - Ilya Kovalchuk - Atlanta Thrashers: Although it might not seem great, this was not a terrible draft choice. Kovalchuk did turn out to be the best player of the draft (which speaks to how weak that class was), annually ranking in the top ten in goals. His return to the NHL has been disappointing, but before he left, he had nine thirty goal seasons in his twelve NHL years, including forty five times, and fifty twice.
2002 - Rick Nash - Columbus Blue Jackets: I can't say this was a bad choice, because the 2002 NHL Draft continued the streak of somewhat weak prospects. Nash did end up being the best player in Columbus Blue Jackets history, if that means anything. In his nine years with Columbus, he had seven thirty goal seasons.
2003 - Marc-Andre Fleury - Pittsburgh Penguins: The simple fact of the 2003 Draft was that it was stacked with future star players. The other simple fact: The Penguins made a mistake drafting Fleury first overall. Imagine if their team had a player like: Ryan Getzlaf, Brent Burns, Corey Perry, Patrice Bergeron, Shea Weber, Ryan Suter, Zach Parise, the list just keeps going and going.
2016 - Auston Matthews - Toronto Maple Leafs: In his rookie year, Matthews improved the Maple Leafs from 69 points and last in the NHL to 95 points and their first playoff appearance since 2013. He scored forty goals that year, including four goals in his first NHL game. The debate going into the draft was Mtthews or Patrick Laine, and although Laine is a great goal scorer, Toronto should be happy with their choice.
2013 - Nathan MacKinnon - Colorado Avalanche: Because of the Avalanche's pick, they have turned from a cellar dweller to a playoff contender. It's really as simple as that. After his first few years in the NHL it seemed like he would be a disappointment, but since, he has blossomed into one of the NHL's best centers.
2010 - Taylor Hall - Edmonton Oilers: The biggest mistake that Edmonton made with Hall was not selecting him, it was trading him away. Edmonton elected to take him above Tyler Seguin in the draft, but six years later sent him to New Jersey in exchange for defenseman Adam Larsson. Imagine having Taylor Hall on Connor McDavid's wing! I guess that is why Oilers GM Peter Chiarelli has since been fired.
2009 - John Tavares - New York Islanders: Not a ton of star power in the 2009 Draft, especially after the first ten or so picks, but Tavares was the best player taken. He turned into a franchise player for the Islanders, but unfortunately could not take the Islanders past the second round of the playoffs before leaving for the Toronto Maple Leafs.
2007 - Patrick Kane - Chicago Blackhawks: Although there were some strong players taken in the 2007 Draft, Kane is clearly the best of them. He's played his entire career with the Blackhawks, he's been to the NHL All Star Game eight times, and most notably, has led Chicago to three Stanley Cup championships.
2008 - Steven Stamkos - Tampa Bay Lightning: Tampa Bay was forced to choose between Stamkos and Drew Doughty first overall. Both have gone on to great NHL careers, and there is definitely no way anyone can say that they made a mistake. On a side note, 2008 really was the draft of the defense, as Doughty, Alex Pietrangelo, Erik Karlsson, John Carlson, Roman Josi, and more defensive stars were all taken that year.
2004 - Alex Ovechkin - Washington Capitals: No two ways about it, this pick made the Capitals a contender for so long, and finally a Cup winner. Ovechkin is the best pure scorer, and arguably the most dangerous player of his generation. He has eclipsed forty goals ten times, and since the 2005-06 season, Ovi's rookie year, he has over 200 more goals than anyone else. The best player in the draft was taken first overall. Period.
2015 - Connor McDavid - Edmonton Oilers: There were a lot of great players for Edmonton to choose from before the 2015 draft, but they knew who their guy was the whole way. Although he played just 45 games in his rookie year due to injury, McDavid has won the Hart Trophy as the league's MVP two years in a row. He was the best pick since Sidney Crosby, and it looks like he might be even better.
2005 - Sidney Crosby - Pittsburgh Penguins: The Penguins might have had the easiest choice ever. Everyone knew that Crosby was the best player out there, and they were right. He has over 100 points five times, has been above a point per game player in every season he has played, won three Stanley Cups in Pittsburgh, and is the best player of his generation.