From 204 series on, each generation just gets worse. The 205 is nowhere as exciting to hear as the 204 in terms of a soulful noise background... meaning it's lost its soul and lost a whole 2.2 liters thanks to beta males dictating emission standards for cars sold in Europe.
Thankfully, the 205 hasn't earned any bad in other areas. In some cases, the 205 is better than the 204. It looks classier, but thankfully it retains that brutish feeling of the 204.
The 206 is what's going to be the fake "AMG" car. The 63 will no longer be a proper AMG. This time around, it'll just be a longitudinally-mounted variant of the CLA45 AMG with a plug-in hybrid motor.
The later 203 and the 204 (and their CLK55/63 siblings) both pushed well above their weight with 5.4 and 6.2L V8s respectively when most of their competitors had 3.2-4.2L I6/V8, with Lexus IS F/RC F having a 5.0L engine (only Cadillac CTS-V and the numerous high-performance Holden/HSV Monaro variants were bigger at 5.7-6.2L).
The 205, especially the two-door variant, is a hard competitor for the inline-6 BMW M4 and the V6 Audi RS5. It's obviously not large enough to compete with BMW M850i or M8, but both of those cars are also too small to compete with the AMG S63 two-door cars. The heavier curb weight and GT feel both make the C63 more of a German version of the Shelby GT350 and Lexus RC F. (I almost said Nissan GT-R, which is very similar in displacement, but that car is AWD).