I agree that Mike Yarwood was probably the best. I really used to look forward to his show each week.
Today's impressionists try too hard, with long drawn out sketches that just become boring and the theme repeated. Debra Stephenson is really good but always overdoes it, especially with Davina. Jon Culshaw & Rory Bremner are the same. Out of a half hour show, there's probably a couple of excellent sketches while the rest is just clever but not funny enough.
I prefer the more "stand-up" type of performance that Yarwood used to do, less make-up with quicker varied delivery.
Alistair McGowan is excellent doing a varied stand-up routine but boring doing the sketch show with Ronni Ancona.
Other impressionists worth a mention are Steve Coogan and Phil Cool.
Must admit I also enjoyed the quick fire impressions from Paul Burling on BGT earlier in the year.
Phil Cool and Paul Burling eh, "where are they now".