As I drive a E60 every day, have E28 and E34 M5's in the garage and recently drove a E39, Ill give you my 2 cents.
Without having driven a F10, I can say hand on heart the E60 is the most amazing of the lot. The E60 gives me the fizz like no other M5 will ever do. The E39 to me has never looked great on paper, it was in my opinion somewhat of an after thought using an existing engine to basis it around. If you look at the Hp per litre this one stands out as being under developed. My belief however its is the best all-rounder in a way that no other M5 can muster (with expection of the F10 maybe). Its the fact that it has low down torque, no performance headers and its power is usable as any other non M motor is on a daily basis. An example being a E36 328i v and E36 M3 or a 130i v a E46. The non M motors are better on a daily basis, you just don't need to rev them so hard to get the best from them. Often M3's don't feel that brilliant unless you're using 9 10ths or more. That can be said of all the M5's too.
E28 - Raw and edgy. Rev's easily and feels willing to go all the time due to the weight, although not that fast. Handling is average and feels outdated. Slightly front heavy. Great fun a 9 10th or more and skids up easy.
E34 - I don't believe Chris Harris, they are a faster and better car than the E28, but I agree they aren't as appealing or fun. The power takes a long time to get past the extra weight +150kg. Far more comfortable, usable and relaxed. Looks a bit old man to me now though. I reckon you could use one as a daily even now if the gas consumption wasn't hopeless 15l per 100k.
E39 - Having spent only 30 mins with one I can say that it would be the easiest to live with daily. Fast but not as fast as I was lead to believe actually. Grunty and torquey. Suspension is compliant and relaxing. Probably would lights the tyres up easy enough and easy to handle with the some what slow steering feel.
E60 - Coming from a place where I dreamt of one of these for 7 years, it has not disappointed. Quick from 0-100, but utterly amazing from 80-160. It is like being on a travelator that low down power just can't give, only high end power can. The world just goes by so fast and were something to happen at that accelleration I'm not sure you could do anything. The gas consumption makes me want to cry daily. You literally can see it dropping in traffic. I get about 22l per 100 each fortnight, but don't drive that far so isn't the end of the world. The SMG is average but having driven a DCT recently, there is somewhat of a manual feel that the later cars have lost. Its challenging but that thump at 8250rpm to the next gear adds to the experience in my option. The things that annoy me is the damn onboard computer always complaining about something and the cost to repair anything. I bought as good as I could which was a very high spec'd 2005 with 90k in the blue I have always wanted. It has the option leather dash, alcantra roof lining, active seats, air con seats and a number of other special bits.
F10 - Without driving one, I'd assume its the best all-rounder, the fastest and probably quite soulless. Nothing about it other than more advanced technology and less running costs does anything for me. Eventually may go there, but I suspect will be forgotten compared to the new F90 4wd.
1.E60, 2. E28, 3. E39, 4. E34
If you want an experience go E60, but don't buy at the bottom of the barrel. Get a GOOD BMW inspection and be thoroughly comfortable and open minded to the expenses.Be prepared to change all brakes $7k, shocks $7k, clutch $5k, bearing $5k and possible SMG pump during its life if it has not already been done. Throttle sensors are also known to be problems at $1k or so each. If its been done or you can wear this, the experience of ownership and 500hp at 8250rpm is simply not replicable in the BMW range in my opinion.
My prediction is that all the rubbish will get neglected and drop in value as people can't keep up with maintenance and can't afford to run them. however the cared for ones will eventually flatten out in value and eventually become super desirable. We might be 10 years away though.
If you want a daily go E39, but it won't give you the fizz that an E60 would.
F10 at this stage is not worthwhile and be prepared for prices to drop when all the fat cat directors offload in 12 months and upgrade to a F90.
My 2 cents, but bare in mind I really know nothing :-)