What isn't there to say about Wario? One of the best things about him is how open ended of a character he is and it's very rarely that you'll run into two Warios that play him the exact same way. His only weaknesses are the range of his attacks, his "oompa loompa" roll that's almost as bad as Yoshi and Samus's, and how he lacks projectiles but these can easily made up by how Wario's fighting style has him constantly in your opponent's face when he lands an attack and how, as the cliche goes, using him is all about mindgames. Dair is too good and can easily be done multiple times even at higher percentages. It's made even better to how dairs can lead into chomp at lower percentages and how those in turn can be lead into a DACUS (ie; the 3God combo or at least that's what they called it the last time I checked.)
Retreating fairs are fantastic as are bairs if you get just the right height. Nair is wonderfully deceptive with its second hit and how it barely has any landing lag and can easily be lead into any attack even if your opponent shields or spot dodges it. Uair is sex on toast if you know how to properly use it close to the ground and it does a whopping 17% damage when fresh. With all this being said, Wario is amazing in the air and this is further highlighted by him having one of the fastest aerial mobility of any character in the game. His air dodge is fantastic too and so is his spotdodge on the ground which can both help make his movements even more deceptive and add to the almost bottomless bag of ways you can throw of your opponent with him.
Wario's throws are about average when it comes to set ups with dthrow easily being the best. It can easily lead to a pseudo chain grab on fast fallers/heavy characters (Wolf, Bowser, DK, etc) and a somewhat of a tech chase for others (Link, Snake, King Dedede, etc). It can easily be lead into dairs, ftilts, and, if you're opponent is slow at the draw, even chomps. Like most people's uthrows, his uthrow is fine and you're probably only be able to create set ups from it (like uairs or even wafts) if your opponent has crap reflexes. Nothing can really be said about his bthrow and his fthrow has a decent amount of strength and can lead to decent chase oppurtunities at lower percentages. Overall, his best "grab" is his chomp because of it's high priority and how it can even have invincibility frames if you do it close enough to your opponent. It's fairly easy to set things up with it and it's versatility is made even better by how it is essentially one of only two "aerial grabs" in the game (the other being Bowser's flying slam).
Wario's specials are pretty out there and they easily make him a more loveable character overall. The bike helps you plow through most projectile spam and quickly cover a lot of ground in a short amount of time. It also helps Wario's aerial mobility as well and allows him to chase recovering characters that would otherwise be too risky or impossible to go after to edgeguard for most characters like a Snake who's almost offscreen using the cypher. Overall, Wario probably has the best and safest non-gliding recovery in the game. Speaking about of recovery, how about that rocket powered fart?
Half charged, it can kill most of the cast at as low as 70% if you do it from above and, fully charged, I believe it can do as much as 45% if you do it from below. It also helps made Wario's recovery even better by acting as an emergency option if his bike somehow fails. Did I mention that, if timed right, it has invincibility frames too? Ironicially enough, his corkscrew attack is among one of the worst recovery moves as it is slow, has a short range, and one of the few recovery moves that doesn't allow you to auto-grab the ledge. It can be somewhat useful if your opponent is crowding you too much, like with Samus's screw attack, but the situation seems to be rare at best.
Wario's tilts are decent for set ups (especially his dtilt) and his ftilt has the best range of his attacks (although that's not saying much). His smash attacks are a mixed bag. His fsmash is his second most powerful killing move (aside from the half charged waft) and has invincibility frames early on but it's also fairly easy to shield grab. His dsmash helps against people who are crowding you and the time the hit box lasts is pretty deceptive but the ending lag is laughably bad and is pretty much a free hit for your opponent if they shield it or if you miss altogether. The only thing his usmash is genuinely good for is his DACUS because, while standing still, it's fairly easy to DI out of especially at higher percentage. Even people who are inexperienced with properly using DI will usually find their way out of this one.
All in all, Wario is a solid character but that doesn't mean that reaching this level is easy. Wario has a high learning curve and playing as him straight forward (as with other characters like Yoshi, Sheik, and Sonic) will more than likely lead to you getting the crap beaten out of you. Personally, I'd compare his learning curve to others that I put in the "high tier" (as opposed to "top") of learning curves like Bowser, Peach, and Lucario. Playing a good Wario is all about screwing with your opponent and taking full advantage of their mistakes. Wario has the tools (high aerial mobility, excellent spot and aerial dodges, orgasmic edgeguard/gimping capabilities) but it's all up to how the player uses him and their brain that determines whether he is high tier or fiddling around somewhere near the middle. This is why, despite many people arguing that he is only top of middle tier (or at least they used to), he has a fantastic tournament record despite his achilles heel of grab releases (especially by King Dedede and Snake) and being able to be infinited by 8 characters (Ike, Captain Falcon, Bowser, Ganondorf, Zero Suit Samus, Yoshi, Peach, and Zelda).