By any measurement, it was historic to see a president resign and to watch a man never elected assume the presidency. Gerald Ford became Vice President when VP Spiro Agnew resigned in October 1973 over corruption accusations.
President Nixon's legacy will always be marked by Watergate. However, his presidency was actually quite consequential:
1) He ended the Vietnam War. I would argue that he won the war and then a Democrat majority Congress let the North Vietnamese & Viet Cong overrun a smaller South Vietnamese army. The post-Vietnam period was not one of our better moments when we left South Vietnam and the region fall under communist rule. Read Nixon's book: "No more Vietnams".
2) President Nixon's domestic record was actually quite liberal, from expanding Great Society programs, to creating the EPA, using executive orders for Affirmative Action and Title 9 for college students. Speaking of his liberal record, Tom Wicker wrote a great book about this called "One of us". It focused on Nixon's career, very centrist presidency and turned out to be a good book to read.
3) Nixon's memoirs ("RN") and post presidency books were excellent.
4) President Nixon's foreign policy was also very significant. He opened up China but the jury is still out on that.
We remember President Nixon and there was a lot more to his presidency than Watergate.