I was doing some internet window shopping on m43 and only found one fast standard zoom? Not a dig, but was surprised. Also cost seems to be greater for some lenses, eg wide angle 7-5 is around 5-600 used, a 10-20 on apsc could be had for 250. There may be some lenses with prices the other way round!
You have 7-14 f4, better and wider than the 17-40 for full frame at a little more expensive new (so yes, more than the 10-20), or 9-18 from Olympus that is cheaper but not as wide. For quality zooms you have the 12-35 f2.8 (17-55/24-70 equiv.), and 35-100 f2.8 (70-200 f2.8 equiv.) so you are covered at f2.8 out to 200mm full frame equivalent with "pro" lenses. There are a host of cheaper non "pro" style lenses which cover 95% of what people will want.
You want to go longer, try the 100-300 (200-600mm equivalent). OK, it's only f5.6 BUT it costs <£400. Show me a 400mm lens on a Canon/Nikon which costs that... the lens choice is very diverse with micro 4/3rds due to two manufacturers working to a fixed spec. and people like Sigma now providing lenses for the system. In fact, I think at last count, there were close to 30 micro 4/3rds lenses available including some f0.95 manual focus lenses (if that's what floats your boat).
The manufacturer "pro" micro 4/3rds lenses are sharper, cheaper and waaaay smaller than the Canon/Nikon equivalents (the 75mm Oly is claimed by many test sites to be the sharpest lens they have - tested period). The 12-35 and 35-100 are as good on a smaller sensor as the Canon/Nikon equivalents are on a full frame and they are
sharper than the Canon/Nikon lenses are on APS-C (the decent FF lenses are designed to be decent on full frame which has a bigger sensor so perform less well on smaller sensor cameras). They are also built very well.
I have a 7-14, 12-35, 35-100 (which is tiny!) and a G5. I bought all new, and still have significant change from trading in my 5D2/L lenses which were sold
second hand. I can also carry all of them around in a bag smaller than one that held the 5D2/24-105
alone, let alone adding the 17-40 or 70-200 in. I have more range, the camera/lens combos take better pictures and I only have 1.9kg
including the bag (just weighed them) to carry around. Try doing that with the Canon/Nikon equivalents (i.e. 24-70/70-200 f2.8s).
The only areas where SLRs work out better are at focus tracking (this will change soon - for static subjects u4/3rds are better than SLRs as the focus is taken off the chip) and if you want very fast long lenses (although Panny are bringing out a fast 150mm next year which will be 300mm equivalent).
I really, truly, believe that DSLRs have limited applicability now. The growth will be in the mirrorless cameras and not the DSLRs. I would advise anyone getting into serious photography to start with micro 4/3rds as you can always do with a small, decent camera for taking out and about even if you decide to go DSLR at a later date.