What I mean by 'comfortably' is that for instance, you can fit 33" tires on 2.5" of lift. Here is my TJ with a 2.5" OME lift on 33" tires (this is before I went to the 4" lift):
View attachment 3580 View attachment 3581
Notice how much less fender clearance / gap I have in these photos versus the ones I posted before with the 4" lift?
Well, that extra 1.5" from the 4" lift made a huge difference.
So, you can put 33" tires on 2.5", but the problem you'll have is that if you like to do a lot of serious off-roading you're going to reduce the amount of flex and wheel travel you have due to the lower lift height.
You'll most likely have to increase the amount of bump stop with 2.5" of lift to keep the tires from hitting the fender, since they're a lot closer.
So yeah, 2.5" of lift and 33" tires will work just fine. However, if you want to take it off-road and get a decent amount of flex out of it, I'd stick to 3.5" to 4" of lift personally.
I'm speaking from experience as well, since I've had both 2.5" on 33" tires and then moved up to 4" on 33" tires.