Taking only major space stations that permit capsuleer traffic into consideration...
Amarr Empire: 484 systems, 998 stations (avg 2.06 stations per system)
Ammatar Mandate: 30 systems, 34 stations (avg 1.33 stations per system)
Caldari State: 503 systems, 1503 stations (avg 2.98 stations per system)
Gallente Federation: 507 systems, 1051 stations (avg 2.07 stations per system)
Intaki Syndicate: 46 systems, 66 stations (avg 1.43 stations per system)
Khanid Kingdom: 23 systems, 32 stations (avg 1.39 stations per system)
Minmatar Republic: 291 systems, 570 stations (avg 1.95 stations per system)
Amarr bloc: 537 systems, 1062 stations (avg 1.96 stations per system)
Of course we have no way of measuring how many other stations are under construction, where, why, or when we can expect them to come online, but the State does have the highest proportion of stations in its sovereign space of any of the powers.
Edit: If nothing else, considering the relative total populations (a few trillion in the State and at least a few times that in the Federation and Empire), we can say reliably that the State has a far lower average population density than the other nations. In terms of stars, of course, it's actually larger than the core of Amarr (Khanid and Ammatar not included).