I wouldnt really mention technical point of view, since most games that used scrolling even on spectrum (and definetly on c64) couldnt use it on CPC because the CPU would have to shift around WAY too much data to be fast enough. Graphically it was about the same as c64 with brighter (and therefore more unrealistic) colours. Games that you mention might look better on CPC (Iron Lord is more or less static, AMC uses 8x8 scrolling which was the same on spectrum and looks awfull, After the war was probably the worst beat-em-up ever on any platform, but there are some gems that you could mention like Gryzor (which lacked scrolling but made up with possibly the best coloured graphics with CPC palette), Chase HQ, Get Dexter, Prehistorik 2 (again no scrolling) and a few others) but when comparing games all-around the c64 wins without any doubt... There are some that will be better on CPC (and ZX) like the ones I mentioned - Chase HQ, Wec Le Mans, even Super Hang-On, isometric stuff like Head over heels, BatMan, etc. but those are really in the minority.
Why did CPC sell so well in France - no idea. I have a vague memory that it had something to do with it being made there and there were less taxes to pay or something like that, but I might be completely wrong.