It depends.
Some kissing in porn is totally over the top, where the lips aren't even touching, they're just running tongues over each other like slobbering dogs and it just seems so unnecessary, and it's so "you're watching porn" that they might as well just go for each others' genitals straight from the off without trying to create a romantic/"getting each other in the mood" facade.
On the other hand a good lengthy bout of kissing where there is full lip contact, no OTT explicit "porn talk" and a decent amount of over-the-clothes fondling is awesome. When a guy (or girl) has been kissing her for a while and there's a gentle squeeze of the bum or a nice slow caressing of a boob, maybe hearing the girl moan softly or gasp a little, I can get hard as nails waiting for those boobs to come free, if the kissing has been a good build up. I watch softcore too so I can get very wound up with well-shot foreplay.
Probably just reminds me of all those times where I was spending ages kissing a girl, feeling that desperate hardness growing and wanting to fuck so badly even though we were both still fully clothed, and looking into a hungry pair of eyes telling me she felt the same, even though it was "just kissing."