I'm filling my tires up to 25psi as stated on the suzuki factory sticker.  The vehicle is totally stock.  However visually looking at the tires there seem under-inflated.  The tire inflator I am using is showing at the gauge it is 25 but can this be wrong?

yes most gauges need to be adjusted from time to time some can't be adjusted though try another one if you think it is wrong don't trust gas station gauges they get dropped to often some tires also have a softer sidewall which will make them looker like they are to low

I'm filling my tires up to 25psi as stated on the Suzuki factory sticker.  The vehicle is totally stock.  However visually looking at the tires there seem under-inflated.... 

My Samurai calls for 20psi and the sidewalls do seem to bulge a bit. The stock tires are rated for about 1800 lbs apiece (max) and the vehicle weighs only about 2300. So reduced tire pressure is required to keep the tread flat. 

Tire pressure gauges lead a rough life. Gas stations have no vested interest in the accuracy of theirs.  You may have to sort though and compare gauges to find a good one.

What I do is run a chalk line across the tire then drive to see how it wore off.  Either add air or deflate until you get an even wear across the chalk line on the tire
The same tire will run different on every car according to weight.

1997 track  my original 205-15 tires called for 23 lb.  I switched to new rims and 235-15 treadwright recaps. run them at  20 lb. so far I am really happy with the results on and off road.

i run 30x9.50-15 with a 2" body lift. i run 22 psi in front and 25 in the rear. (the tires say to run 44 psi cold) i like the way they bite, and they look just fine, but bump steer and death wobble is a bitch only 35 mph. trying to figure it out i put on an old man emu steering stablizer, and 2 degree caster shim, and still cant lick it. just short of installing new knuckle seals, i found 32 psi and 35 psi helped alot. but i still think i will instal the knuckle seals.

i have some thoughts about tire pressures:
first is what pressure you actually have(re:gauges), and what is good for the tire(which depends on how you're using it), then what is best for the vehicle.
my sidekick(susie the psychic) had 205/75R15 at 23psi F&R. that is stock as per manufacturer. supposedly they tested that.
tire dealers would put 35psi in 'em, but they sell tires. suzuki figures it handles right at 23psi. i go with suzuki.
i think same psi F&R makes sense, 'cause it would tend to oversteer, rather than understeer as it looses traction, due to the slightly heavier rear.
currently i run 31x10.5R15 at 22psi.
suzi is slightly heavier than stock, but balanced about the same- i did some "fuzzy math" and came up with  775 lbs/wheel.
the tire says it'll be good to 2270lbs/50psi- more "math" indicated i could run 18psi.
so then i use the gauge i like best. i run slightly higher(22psi) on the road. more like 12-15psi off(sometimes lower).
i've done this for years with many different vehicles/tires.
there should be a weight/tire size/psi data plate on the rig, and the tires have the weight/psi info on them.
just a thought.

also: the chalk thing is good, alignment helps. too much air wears the middle. too little works the edges.