RIP David Warner, your voice acting was amazing.
I can understand why this game is so well revered. I do think it's a tad over hyped, but only a tad. This continues sometime after the events of the first game where you awaken imprisoned. Jon Irenicus is experimenting on you, and it is basically torture. His "experiment" is interrupted by a raid from a rival gang and the story begins. I actually enjoyed this tutorial dungeon. It certainly is complex if you aren't familiar with Baldur's gate. For this reason, I think it's a bad idea for a new player to the series to start with this game. Not only are you thrown into a relatively complex dungeon, which is honestly more complex than most dungeons in BG 1, but you also start at a higher level.
While that might sound appealing, AD&D is a very complex and dense system. BG 1, by starting you at level one, eases you into it. If you are playing a mage, and you start with Imoen who is a mage, you will find it overwhelming trying to pick your spells. The spell descriptions are about as good as they can be, but that doesn't make the potency or utility of a spell self evident. You will likely spend a lot of time googling "best spells" and reading through various forums where people debate. This game came out at a time before reddit and as a result there really isn't a central location to go for useful information. That said, I highly recommend this website: https://lilura1.blogspot.com/2021/01/Baldurs-Gate-2-BG2-Best-Mage-Spells-Best-Sorcerer-Spells-Ranked-Tier-List.html
I included the subpage for best spells to make it easier for new players. That website does cover BG1 as well so it is a very useful source.
That all said, what has improved? The side content is a huge step up from the original BG. The side quests are varied, usually layered with sub-plots and can lead to surprisingly sprawling areas. Most companions will have a fairly intricate opening quest you get while recruiting them. I enjoyed all of these and spent the first 40+ hours just doing side quests. Yeah... there's a lot. But hey they are completely optional (mostly). The first major quest you get, once you escape Irenicus' folksy abode, is to fund raise 20k gold. One thing that may turn off some players, it took me aback briefly, is you are completely stripped of your equipment and gold from BG1. All that imports over is your characters stats and abilities. You get some items from your first playthrough, but only a few. I like this decision. This first major quest encourages you to go explore the world and side content. After doing two side quests I had enough funds, but I was so engaged with the questlines that I kept going until I completed all the quests I encountered.
Exploration is kind of a mixed bag this time around. On one hand, you no longer have to walk through adjacent locations to reach a new location. Instead, you can immediately fast travel to a new location. This removes a lot of the early game loop from the first game. You spent a lot of time walking from left to right, or top to bottom, vice versa. A lot of the map locations in BG1 were mostly empty with a few locations of interests or items. With the inclusion of fast travel, the maps are now more densely packed. There doesn't really feel like there is any filler anymore, in terms of locations. The reason why I think this is kind of a mixed bag, is you are essentially warping around which makes travel feel less like a mechanic. I don't hate it, but I can understand why someone may prefer BG1's system, where you need to traverse to a location first before you can fast travel.
Gameplay is mostly the same as the first, but... you are high level. This drastically changes how you approach encounters. The early phases of BG 2 are the hardest, which may seem counterintuitive. The reason for this is "power creep." After a certain point, when you get high enough level, and you have at least a few mages in your party (I had 3 mages) you become unstoppable. Mages are just so busted at high levels. As long as you are fine with tediously buffing your party with every buff and using a few spells in combat, you will blow over anything. A enemy mage or lich buffed himself to be invincible? No problem, Breach or Dispel. Now he falls over like a paper doll. The cheese tactic of setting a bunch of traps and skull traps still works here too. I killed every Dragon in the game (except for the Silver Dragon) with this strategy. They all died in one hit, but it took me 5 mins of spamming abilities and resting to prepare. Mindflayers can be challenging, but if you use Chaotic Command, you become immune to their crowd control effects and can smack them to death. So combat is more complex, but easier if you are willing to engage with it. My first playthrough I soloed as a fighter/mage/thief. For BG2 I decided to switch things up and use a full party. While I like a lot of characters in the game, companions are still fairly bare bones compared to bioware later games. After their initial quest and potential follow-up quest (most companions seem to have two quests) there isn't much engagement with them other than banter. That does add flavor and this banter can sometimes be between party members which is a nice detail. having Keldorn try to calm down Minsc was amusing.
The overall story I do think is weaker compared to BG1. While both Irenicus and Saravok have a very similar arc and goal (both basically committing genocide to become a God), I do think the plot of BG1 fits together in a more coherent fashion. BG2 feels more like a pulp novel in comparison. A greatest DnD hits, which is fun, but contrived. You will fight droves of Mindflayers, Behoulders, Vampires and Liches. While this is cool, it doesn't always make sense how often you find a Beholder and Mindflayer colony literally right next to each other and both underneath Amn which is strongly anti-magic... wtf. It is cool, but doesn't really make sense narratively. Like the Cowled Wizards are fucking up so hard with this large underground network of evil.
Irenicus' motivation and goals are all pretty petty and simplistic. He basically tried to become a God, which almost killed his entire people, was banished for it (for good reason obviously) and was so made that he decided to do it again. He really isn't a complex character. To be fair, neither is Saravok but I think each plot thread feels less contrived compared to BG2. For example, it really doesn't make sense why Irenicus willingly let himself get captured by the significantly weaker Cowled Wizards. In the clip above he effortlessly kills most of them. The game "explains" it by saying he was testing the PC and using Imoen as bait. Needlessly complex and contrived IMO. Why not just recapture the PC and begin his experiments a new? Most of the plot is basically a case of Carmen San Diego globe trotting around and following Irenicus. Even Irenicus stealing your soul feels completely contrived and meaningless given when he enters the Elf city he still needs a priestess to connect and steal the Life Tree's essence... in addition, nothing really changes mechanically once your soul is stolen. You are as powerful as before but can turn into a berserking Demon. Irenicus was already powerful and the game doesn't do a good job of showing him being more powerful. It just seems like all he needed to do was get the drow to start a war and mosey on in to the Elf city to become a God. That said, each globe trotting subplot is good. I enjoyed each thoroughly. It's just a shame that the connection between them feel contrived.
In conclusion, a great sequel. I don't think it is as strong as the original, due to more plot contrivances and the power level of the PC. The power trip is likely appealing to a lot of people, but I find low powered DnD more enjoyable. Still worth checking out, but I recommend starting with BG1 first, otherwise you will be overwhelmed.