Just had a quick glance at my rack:
25mm gets used all the time: I have two, one as a "beater" (cutting socket boxes in plaster board, taking up floor boards (I'm a sparky)) plus a second one for cuting hinge/mortice lock recesses.
1/2" for tidying up mortice lock "pockets".
1/4" for fiddly work.
Plus I have a 1/8" for those awkward jobs.
Realistically, the answer to your question depends upon what work you're doing:
A couple of years ago, making pergolas, my 2" chisel was used all day, every day, and none of the others got a look-in