(i) It's clear that Deadfire used BG2 as a frame of reference. They deliberately incorporated aspects of BG2 that made it such a success:
- embarking on a quest to reclaim your soul, from an immensely powerful antagonist, whose motives are one of the game's major mysteries
- importing your character and continuing their story
- being moved south of the previous game's standard "high fantasy" setting, to a vaguely exotic new setting
- a stand-out "big city" packed with interesting locations, quests, and secrets
I think it was a great idea to use all of those guidelines. Deadfire's quest-design reaches the level of BG2 at times; Neketaka, for example, is the best successor to Athkatla I've ever encountered. Hats off to the devs for the excellent work they did in this regard!
(ii) However, Deadfire also has a major problem, especially when compared to BG2: the main storyline (the "critical path"). Other people have discussed it in detail, but I'll give my own thoughts.
If you took out BG2's sidequests, then its critical path still stood on its own as an epic journey and compelling story; it constantly surprised the player (Chapters 4 and 5, the surprise final battle in Chapter 7).
By contrast, Deadfire's critical path does not work on its own. It is short, uninteresting and repetitive. Without spoiling anything, imagine if BG2 had ended at Spellhold; Deadfire feels like it ends at the halfway point of the story.
Irenicus was also a particularly interesting and memorable villain; as one review put it, he stole the show whenever he was on screen, and his backstory was arguably more interesting than your character's. There was a Gamespot "Top 10" list for villains, with well thought-out guidelines about what makes a good villain. I remember thinking that Bioware must have used that list as guide -- because Irenicus was pretty much the perfect villain. Who can forget his dream sequences? "Life...is strength."
For a giant green statue, Eothas' presence is barely felt in Deadfire's storyline. I think this can be fixed through the addition of some dream sequences (at least one for each act), like Irenicus' in BG2. But Eothas is also a polite, mild-mannered gentleman compared to the cold, ruthless Irencius.
(iii) I think the other major difference, compared to both BG2 and Pillars 1, is the real-time world map.
Its art style is too -- for lack of a better word -- "cartoony", with its bright colours. I understand the need to distinguish Deadfire's lush setting from the bleak Dyrwood, but it should still be consistent with the "realistic" art style.
The real-time map also turned travel on the world map into a tedious chore, whereas the instant travel from the first Pillars (and on the city maps in Deadfire) works just fine.
I think travel problem can be fixed in two (somewhat opposite) ways:
- making the world map more interesting (random text interactions, as described in my signature)
- adding a "fast-travel" option
I certainly enjoyed the game, and hope they will finish the trilogy with a crowdfunded Pillars 3.