I love Rhodia. Nice and dense, they come in 80 and 90 gram. There are dot pads, graph pads, meeting notebooks, large square pads. I use them all the time for work. And, they are pretty inexpensive.
Tomoe River 52 remains a top favourite - I have a couple of notebooks left, so should have it for a while. Have a couple of TR68 notebooks as well.
Cosmo Air Light is a close second - brings out ink properties beautifully and can take a lot of abuse.
The best value for money I've found though has been the Nakabayashi Logical Prime notebooks. The paper is fantastic, and the notebooks are priced decently.
looking up tomoe river after seeing yours and others’ comments, it looks like they’re discontinued :-( i will have to pick some up on ebay or etsy though, since so many people like it!
Hobonichi notebooks and planners are all Tomoe River. So are Endless Recorder notebooks. Galen also has notebooks in TR. Now is a good time to get TR - it is still available in many places :)