The problem with breast expansion for this type of thing is the workload increase on the devs. A single stage of BE is equivalent to an extra set of CG that needs to be prepared, so you could understand how the amount of CGs can get out of hand quickly. It's one of the reasons why games like paizuri slave training program are so rare. That's for games with a BE variation throughout though, it's not too much work to just have a couple of scenes though. Add on top the fetish being niche. Also, It's easier for 3D models to have some sliders cranked than for entirely new 2D art to be produced.
So essentially you're asking for the cream of the crop BE games, the exceptionally rare gems produced by people more dedicated to the fetish than just adding some extra scenes. As somebody that doesn't like 3D renders I know of a couple, but I'm also going to recommend a few that aren't "pure" BE games but have a decent chunk of BE content.
Lots of BE content
Legend Of The River Queen ~Goddess of Inzu Peninsula~: Every fish has two extra forms, BE and pregnant. Quite good, you need to MTL it yourself (
AdventCirno MTOOL is fantastic). This game is a sequel, previous game (which I can't find a thread on f95 for) has BE too, this one is better.
Lilia's Livelihood: One of the rare games that is 2D with persistent BE stages and art for everything. Only bugs/tentacles/monsters abound, but really good if you don't mind that. Dev has two other games,
Rain's Rave and
Nursery Dimension. Lilia's is better than Rain's Rave imo and only play Nursery Dimension if you're desperate.
Aikagura: Only one enemy has a BE attack so far as I remember, but every game over scene varies with BE. It's 2D with spine animations and that lets devs have the same slider like controls of 3D models without looking 3D. Bigger tits without a tremendous workload increase. Get the latest patch in the thread, lets you increase the max size in the gallery substantially.
"Bigger tits" mode
Sol Rui -after mini-: School route lets you access two stages of BE, applies to every other scene in the game. More of a a "bigger tits mode" than a BE game, but it's incredibly good.
Crisis Point: Extinction: Another case of western devs being incompetent Patreon milkers. What's there is pretty good, lots of high quality "bigger tits" scenes. Don't get invested in the development of the game though.
Has BE, worth trying
Monster Black Market: Not actually a BE game but with some mods it works pretty well as one. There's a mod for a bigger max size and another that lets you tweak stats with the tentacle rooms, including size.
UnHolY ToRturEr: Same dev as Aikagura. Less content still good, BE only really prevalent in the DLC.
ErisDysnomia: One of the rare few games so good I come back to play it every so often. Very good game, not all that much BE content. What is there though is incredibly well done, 11/10.
Ayura Crisis!: Same dev as ErisDysnomia, same deal. Very good, not much BE, what exists is very good.
Eggs of the World-Phantom Lilium: Has a level dedicated to BE, as well as some BE in other places.
The previous game has some BE too but not as much.
There's other stuff out there with a scene or two of BE content that's still good. Like the Acerola games or any of the action games by NappleMill. Melty's Quest has a BE costume. I could think of more but it's straying off topic.
