How is Diablo and street fighter?
Diablo is awesome. The story and cutscenes are engaging and I'd say pretty deep. There's plenty to do, but once you beat the main story, as with most ARPGs the game becomes a grind, if you're not the type of person who likes grinding to get the best gear and continuing to power up your character to handle harder content then it may become a little bit boring for you, but the things to do after beating the main story are:
Side quests: Plenty to go around in each city, some of the stories for the side quests are more than just simple go kill shit, etc.. Like for example there's one about helping with an exorcism of a kid, etc..
Renown: Probably the most tedious of the bunch but it's worth if you want the extra points to build your character, it involves you getting enough points in a city by discovering enough of the city's areas, waypoints, lillith altars, dungeons, and more.
PVP: There are pvp areas where you can fight other players and get things that are pvp exclusive
Helltides: Pretty fun, areas of the map randomly become a helltide for a certain amount of time, like 30 mins or so. During which your goal is to kill as much as you can, collect cinders from those kills, then use the cinders to open hidden chests that contain loot that often contain legendary gear.
World bosses: Also fun, they spawn 4 times a day; somewhere around every 6 hours. Players can all collectively fight world bosses together as long as they're in the area and get good loot. Last one I did was with me and like 15 other players.
Dungeons/Nightmare Dungeons: Regular dungeons often have rewards that unlock "aspects" for the character classes, aspects are special abilities that empower your character and can be imprinted on your gear, so your character can have multiple aspects on at once. completing them also help towards your renown in the area you completed them in. Nightmare dungeons are harder versions of dungeons where the monsters are buffed and often higher levels than you, but they drop higher tier loot than legendary and also give point to power up some of the endgame related skill trees to make your character stronger.
Other than that, you can group up with others and complete quests, dungeons, etc.. together and have a ball. You finish the main story usually around lvl 50. I'm currently lvl 57. Seasons will be starting soon, as with most ARPGs, you start every new season with a new character that you're able to get exclusive seasonal content with. The stuff you get from seasonal content you can send to your non-seasonal characters so it's worth it to play them.