I would rate Richardson as 'one of New Zealands best ever' - probably being third choice for opener after Bert Sutcliff and Glenn Turner, and then only being edged out by lack of big scores (while still being comparable in average). Arguably Martin Donnelly could be ahead of him too but it's hard to tell as he didn't actually play that much test cricket and his legend is based more on eye witness accounts from Oxford.
The main things about Richardson's career aren't easily readable from the stats, it has to be put into context; not only did he normally average 10-15 more runs per innings than anyone else in his team (consider that more renowned NZ bats such as Fleming and Astle don't even average 40) but he provided a huge amount of stability to the NZ innings. There's one of those 'stats don't tell the whole story' pieces on cricinfo to this effect:
http://content-nz.cricinfo.com/newze...ry/135980.html
I can still remember a shocking day at the basin where NZ were running along semi-comfortably with Rigor at the crease. Then he got out, we lost about 7 wickets for as many runs and turned a 170-run 1st innings lead into a 6-wicket loss. I'm sure many more examples could be found if you dug deep enough [i just saw these are in the above article, sorry, i didn't read it before pasting in the link]
Yes he was dour, yes he was boring to watch, yes in the amount of time he spent at the crease any of his contempories would have scored a pile more runs/tons (a lot of his innings were 70's/80's/90's) but he was invaluable to the NZ team in a way those players had the luxury of avoiding