Even though many will disagree, Campbelltown is the logical location for a new stadium, here is a comparison between Campbelltown and Parramatta.
Access by road:
Campbelltown: Ease of access by road - Major highway minutes from location, small upgrade to local roads would improve access even more.
Parramatta: Access by road issues - Even though the M4 is located close by, it is one of the most conjested motorways in Sydney, added to that Parramatta Road and Woodville Road are car parks most of the time.
Access by public transport:
Campbelltown: Majority of the rail network can access Campbelltown without changing trains (Liverpool/Granville and East Hills/Airport lines), for major events Bankstown and Western lines could also have direct access as the infrastructure is alread in place)
Parramatta: Not all areas can access, Campbelltown can however anyone on the Bankstown or East Hills/Airport lines would be required to change trains.
Growth area:
Campbelltown: Is located in a large growth area, which will continue to grow over the next 50+ years, as such there will be an increase in youth in the area and a major stadium would be beneficial to the region.
Parramatta: Already near capacity, though areas around Penrith and Blacktown are growing Parramatta is not the hub of this growth. As such Penrith or Blacktown would be more suitable for stadium.
Existing stadiums in region:
Campbelltown: Local stadium, no large sporting arenas within 30 minutes of area by road or public transport.
Parramatta: Local stadium, large 80,000 seat multi purpose stadium and 25,000 seat oval stadium within 10 minutes of location by both road and public transport.
Other options: Blacktown/Penrith - Though in high growth areas, access to the area is not easy compared to the other two major options, major upgrades to transport and roads may be required.
Though Campbelltown may not be of use as a stadium for multiple teams (Tigers and Wanderers would be most likely tennents) the ability of Olympic park to be utilised by Parramatta and the Bulldogs mean that it is more suited to them. But the simple fact that Campbelltown is in a region that will have some of the largest growth in the near future plus being idealy located in comparison to other major sporting grounds it seems to be the option (though I believe that either Parramatta or Blacktown would be the frontrunners at the moment).
But that is just my opinion.