Not a huge great deal of pizza places that I love in Glasgow unfortunately. Bier Halle on Gordon Street is good - it is a basement bar, predictably in the style of a German beer hall. It is noisy, often busy and not good for kids (don't know if you are with children or not) but the pizza is pretty tasty!!
There are a couple of pizza places in the Merchant City - The Italian Kitchen for one - not cheap if I recall correctly, but quite tasty. There was also one called Qua which was OK a few years ago though not sure if it is great now. Aside from Qua and the Italian Kitchen, there is one pizza place that I recommend you avoid - but I helpfully can't remember its name. OH went for dinner there after a meeting - said it was stodgy, greasy and he felt quite icky after eating it for the rest of the night.
Paperinos is meant to be good - think that may just be in the West End now on Byres Road. If you are down that way, Little Italy is good on Byres Road too, but it is not really sit in and though it is great, it is not the style of pizza I prefer.
If you want to go for a chain, Pizza Express on Queen Street is not bad at all either.
To be honest, Glasgow has some fab restaurants - I'm just not sure if Pizza is done that fabulously!!
Sorry that I couldn't be more definitive/specific - just saw that you had no replies so hoped this might kick off discussion!!
43 New Oxford Street, London WC1A 1BH, GB