My best commute was either in my first year at university (2 mins walk) or 2nd year (10 mins walk, mostly on a beach).
That apart, I found c2c's 357s quite acceptable. Not massive seats (and as I find now...those seats are way less comfortable than the ones on Stagecoach Gold...), but amazing massive windows, air conditioning that usually worked, and a nice non-stop run from Benfleet to Fenchurch St (or vice versa) that could be good reading time.
I can't argue with the FGW HST from Oxford to Paddington on those days (regular but not daily) when that forms a large part of my commute. Large, reasonably comfortable seats,somewhere to plug in/charge laptop or mobile phone, and so on. Some may criticise the high-density seating arrangements, but they do mean (on this route anyway....) there are usually enough seats to go round. And a coffee trolley too.
Absolutely worse commute I've ever done regularly: the Northern Line by some way. Crowded, overheated, cramped,g generally unpleasant. (The grotty old 508s or 313s on the grotty old Silverlink Metro into Euston might qualify, but the service was so unreliable I tended to not use it, despite the station being at the top of the road on which I lived then)