To add to the statistics from Zaremba and PEWS, Cricinfo did an article on Grace a few years ago which I bookmarked and makes for more interesting reading:
WG Grace: stats analysis | Specials | Cricinfo Magazine | ESPN Cricinfo
• In 1871, aged 23, he scored 10 centuries and 2739 first-class runs at 78.25. The next best average was 37.66 with just one hundred.
• Even 31 seasons later, he scored 1187 at 37.09, while Victor Trumper, at age 24, averaged 48.49 (Trumper's best season).
• In 1876, he scored 839 runs in a mere eight days, with a sequence that read 344, 177 and 318 not out. It was a season when only one other batsman topped 1000 runs. His 344 was also the first triple-century in first-class cricket.
• Between 1868 and 1880, he topped the first-class averages 10 times, including seven times straight till 1874. Between 1868 and 1876, he scored 54 first-class hundreds; the next highest didn't even manage 10.
• In the decade 1871 to 1880 he averaged 49, a period during which nobody else averaged more than 26 or scored even a third of his runs. He also took 1174 wickets in the 10 years, which was the second-best in the country after Alfred Shaw.
• In 1895, as a 47-year-old Grace reeled off scores of 288, 52, 257, 73 not out, 18 and 169 - the last bringing him 1000 runs before the end of May (the first man to reach that landmark). His 288 was also his 100th century, making him the first player to the milestone.
• Grace played 870 first-class matches in his career, which is the third-highest on the all-time list, after Wilfred Rhodes (1110) and Frank Woolley (978). His tally of 54,211 runs is the fifth-highest, while his haul of 2809 wickets puts him in 10th place.