I'm pretty sure everyone knows about this one but Sword Art Online is an amazing anime.
Sword Art Online has its epic heights and quite a few entertaining moments, but for what it is, you're better off watching it at least through the first arc. The second arc drops any bits of scant integrity and semi-competent writing the show had and tops it off with a **** strudel of cliches, cringe, and asspulls. I will say that if you want to watch SAO II, at least the aftermath of the second arc is important to understand the story.
TL;DR If you are interested in SAO, best to watch it whilst watching another show. The substance will hit you quick.
Anyways, some personal recommendations, which you can take based on what you like:
Fate/Zero: Adapted off a series of novels within the Fate/ franchise of light novels, Fate/Zero is a prequel to the franchise inhibitor, Fate/stay night. Without getting overly elaborate explaining the plot and setting, there is a magical ritual called the Holy Grail War that is performed by three clans of mages in order to seek the victor of the Grail War's one true wish. Eight masters are selected by the Grail and they must summon 1 servant from the 8 classes (Saber, Archer, Lancer, Rider, Caster, Berserker, Assassin). There are a lot more rules to the Grail War that make it easier to understand, but I won't get into them. The series is a rollercoaster of action, subterfuge, and philosophy that hits you with all sorts of twists and revelations from start to finish. Besides a bit of Inaction Sequence here and there, the fight scenes are some of the most gorgeous and fluid I've seen in recent memory. The strategies the characters employ are actually intelligent. Not to mention the society it crafts, where how
magic magecraft works and operates so well that it would be believable coming out of a textbook. When most media wants to hit you over the head with an anvil of heroic philosophy, Fate/Zero deconstructs concepts of heroism, kingship, etc., and gives some compelling food for thought. Just be warned is pretty dark (written by Gen Urobochi) and it won't reel back its boot when there's a dog to kick. Nonetheless, this is one of my favorite animes of all time.
Black Lagoon(: The Second Barrage): This action seinen date by a good decade and a half like most other anime of the 2000s boom. In fact, it's currently being shown on Adult Swim, which reels a lot of new viewers in. Black Lagoon revolves around the misadventures of the Lagoon Company, a group of pirate mercenaries offering their illegal services in Southeast Asia. This show takes you into the underbelly of the criminal underworld of Roanapour and beyond. You'd think its corrupt setting would make the show too chaotic and stagnant. But the interactions between the characters and various crime syndicates make it more of a community with its own inclinations. If you like Cowboy Bebop, the semi-episodic format and character concentration will pull you in. The main cast is entertaining enough and offers opposing shades that serve to compliment each other. I'm sure you may be familiar with series postergirl, Revy, the ****-talking, gun-totting, depraved mercenary. She has to be one of the most begrudging anime characters I've ever seen. She comprises everything I hate. Yet she pulls it off so convincingly that she is somehow enlightened by her dark aura.
Puella Magi Madoka Magica: The Neon Genesis Evangellion of the magical girl genre. I mean, freaking Gen Uorbochi wrote this baby! It's about a group of teenaged girls who find a cute little creature called Kyubey, who grants them a wish in exchange for awesome magical powers to fight evil entities called witches. It plays itself as straight-faced as it sounds, until you realize the fight for survival really taking place. The sugary, whimsical set pieces and moe character designs brilliantly juxtapose the gritty, depressing atmosphere that hides beneath, gradually surfacing. The girls may not be the most developed heroines, they're pretty likable and you may come to feel sympathy for them as they endure the grief they're subjected to. It's around 12 episodes, so you will be able to finish it within one day. This does not count the 3rd movie, which continues the story, but may screw with your perceptions of a certain character after the first series ties its threads by the end.