Kohl was just one of several conservative, anti-Communist Western leaders in the 80s, overshadowed by Reagan and Thatcher. Merkel is the leader of her own little bloc though. She's a leader in global politics rather than a passenger. She will be a larger figure in history than Kohl for sure.
Of course that's also a result of a Germany changing from a country the size of France or UK to one significant stronger with their own sphere of influence to the east (which ironic are welcomed today, I think Merkel really need to thank both Putin and the French government, for the northern east Europeans seeing Berlin as representants for their interests).
That may not last that much though because Germany is losing population while France gains.
If the current pattern is sustained then in a few years the latter will surpass the former not only in terms of population but also of GDP.