I'm not a huge motor racing fan but I agree with others about Murray Walker's infectious enthusiasm for his job. His well-known gaffes added to his great attraction. When I was growing up in the 1950s I remember his father Graham Walker, a former professional racing motorcyclist, commentating on that sport on radio, particularly the Isle of Man TT Races. There is no doubt that Murray brought great pleasure to so many people with his knowledge of motor sport and the supremely entertaining way in which he carried out his work. RIP.
As to JENNY's point about respected voices in other sports, several have already been mentioned who would be on my list.
Football: For all its great popularity football seems to produce competent technicians rather than great commentators and writers, particularly with tv and radio. Older people will remember Kenneth Wolstenholme ('They think it's all over......it is, now!') who was BBC Television's voice of football through most of the 50s, 60s and early 70s. I think the current bunch of football commentators are a pretty bland lot. If I had to pick one to represent the spoken and visual football media in my lifetime it would be Brian Moore (not rugby's Brian Moore) originally on BBC Radio but ITV's main football commentator and presenter from the late 60s until the mid 80s. He was hugely respected within the game.
Cricket: Richie Benaud by some way for me. As astute a captain as ever donned the Australian baggy cap, he missed nothing when commentating in later years and had such a simple but complete way of explaining even the most complex cricketing conundrums. John Arlott was cricket to many around the cricketing world from the late 1940s until 1980. He had a wonderful gift of description and that Hampshire burr was somehow so apposite, redolent of watching cricket on a village green on a warm summer afternoon. Probably not many know he had been a policeman for ten years, then a BBC radio poetry producer before becoming radio's undoubted cricketing king, later to branch out into television especially BBC 2's Sunday afternoon 40-over per side matches, but radio was his true metier. He was also a wine connoisseur - in his later years possibly a little too fond of the grape - and a marvellous writer on cricket, wine and other subjects. He was at the microphone when the first streaker appeared at Lords. He described him as a 'freaker'. That commentary can still be heard on YouTube. Then there was Brian Johnson ('Johnners') - very knowledgeable about the game and he punctuated his commentaries with almost schoolboy humour with 'jolly japes' making frequent appearances. He was involved in the 'leg over' incident with Johnathan Agnew when both dissolved into uncontrollable hysterics live on air that caused motorists to pull over to the kerb because they were themselves laughing too much to be able continue driving safely. In his early days of commentary 'Auntie' BBC was still very straight-laced but Johnners got away with this one in the 1960s: New Zealand had a bowler called Bob Cunis of whom Johnners said, "Funny sort of name, neither one thing nor the other'. He also asked Rachael Hayhoe Flint (later Baroness Hayhoe Flint) former captain of the England Women's team if lady cricketers wore boxes when batting. 'Oh yes' she replied, 'but we call them manhole covers'. Rachael had a wicked sense of humour and I think the two of them set that one up beforehand.
Rugby Union: Surely there can be no other contender when Bill McLaren's name is mentioned. He was the voice of tv rugby union for much of the second half of the 20th Century. His Scottish Borders accent was such an easy listen and his one-liners were legion: 'He’s like a demented ferret up a wee drainpipe'.
Rugby League: Bill's contemporary in the 13 a-side code was Eddie Waring whose name was indelibly associated with the game for 20 years from the early 1960s. As far as many people who didn't follow the game closely were concerned, especially in the south of England, he was rugby league, through his commentaries on club matches shown live on the BBC. His eccentric style made him a great favourite of tv and radio impersonators. For someone so closely identified with rugby league, Eddie Waring's game was actually association football as a young man and he had trials with a couple of Football League clubs.
Briefly, some more:
Golf: Peter Alliss
Tennis: Dan Maskell
Boxing: Harry Carpenter
Athletics: David Coleman, although he was also used widely as a football commentator at major matches, and was well-known as the presenter of BBC Tv's live Saturday afternoon sports programme Grandstand.
Many thanks JENNY for giving what passes as my rusty old brain the opportunity to oil the nostalgia cogs.