Rugby borough area is 100,000, not Rugby town. Nuneaton is a bigger town. Rugby town population is nowhere near 100,000 .
Rugby town centre has suffered in part because of the redevelopment of Elliott fields and Junction 1
Coventry city centre has been utterly crap since world War 2. Awful planning. Lack of investment. For a fairly major city it's pitiful.
Of course Cov City centre has its issues, and part of that was the 'futuristic' planning post-war that has proven to be unsuccessful (and warnings were given about it, but at the time it did prove popular). Much of the residential was moved out and so the city centre lost being used as a community hub. The increase in student accommodation has rectified that a bit, though can be seasonal. The ring road (while useful) was badly designed and massively puts people off. I'm sure a similar city centre bypass could have been designed that was less intrusive and used up less space. The precinct was OK (though they stuffed up the design of the split levels), but when the initial design got ruined by stuff like the escalator, Cathedral Lanes etc it lost its main appeal. The recent changes have made it more like it was envisioned and so might actually become more popular again, though it will probably have to move on from being solely retail and into entertainment/leisure and dining.
The history of the city and its heritage buildings are spread out, due to both bombing and planning, so you can't create that olde worlde feeling and benefit from tourism, and being stuck slap bang in the middle of the country isn't enticing.
Some of it though has been due to the way the fortunes, size and layout of the city. Coventry has Birmingham as a bigger competitor, so many brands will go there first. With the industry going tits up in the 80s/90s the earnings of the residents wasn't high enough to attract high end retailers. High earners in Cov move to Warwick/Leamington/Kenilworth and so higher end retailers go there.
A lot of the industry that closed left huge areas of the suburbs derelict and so to provide jobs these became retail parks and offices, moving traditional city centre businesses out and thus the city centre became unused. Ironically, the one retailer that absolutely suits a retail park is IKEA, yet we moved that into the centre, which was utter madness. Even stuff like C&W Hospital moving took away some footfall, as did CCFC moving.
I've got a load of ideas that I'd do given the chance, especially Broadgate and the Precinct, but most importantly I think we need:
1. look to close some of the retail and office parks (esp. Central Six) and entice these retailers back into the city centre. This would then free up land in the suburbs for housing.
2. Look at ways to redesign the RR so it isn't so offputting and intrusive, psychologically cutting the city centre off from the rest of the city and reducing the number of people that use it. I'd also consider looking at ways to alter the junctions so that some are dedicated to joining the ringroad whilst others just go into town.
3. On a similar note, complete the outer ring road to the north west, reducing pressure and traffic on Holyhead Road, Allesley Old Road etc. Also look at opportunities to widen the roads that link to the ring road.
After that I'd consider connecting those roads that dead end due to the ringroad together (i.e. connecting Lower Holyhead Road to Spon St) and placing buildings next to the ring road to reduce its impact.
Cost wise the next one would be unfeasible, but moving the older buildings to an area near the three spires to create a heritage zone which would enable the city to better sell itself as a historic place. Could also be used as an educational Living Museum with a retail aspect of selling items made.