Roddick was far more convincing against his biggest grass opposition (Fed) than Lendl ever was against his (Becker). He made more finals, and came much closer to actually winning.
If that weren't enough, Roddick always had the tools to be successful on the stuff, while Lendl had to play well outside of his comfort zone to stand a chance. He served-and-volleyed on cruise control every time SW19 rolled around and was passed before he could even look up against any of his biggest opposition.
Why are you such a clown of a poster these days?
You must not have watched Wimbledon in 1989. In the semifinals, Lendl gave Becker all that he wanted and more before the German prevailed in 5 tough sets, 7-5, 6-7, 2-6, 6-4, 6-3. Indeed Lendl might have won the match if not for a rain delay that Becker himself acknowledged allowed him to regroup. Moreover, this was Becker's finest fortnight. The 2 sets dropped to Lendl were the only 2 that he dropped over the course of the tournament, which concluded with Becker beating Stefan Edberg in straight sets, including a 6-0 set. This was the same Edberg who would beat Becker in 1988 and 1990 in the finals.
It was also the Edberg who Lendl beat in the Wimbledon semifinals in 1987, a year in which the Swede won the Australian Open on grass and a year before he would win his first Wimbledon crown. During another year that Edberg would win the Australian Open on grass -- 1983 -- he would have to get past Lendl in the semifinals, 9-7 in the fifth set.
Furthermore, while Lendl never could get past Becker at Wimbledon, including a loss in the 1986 finals, he did crush him, 6-3, 6-2, in the Queen's Club finals in 1990, the second straight year that he would win that title.
There's certainly a case for Roddick being the best bridesmaid ever at Wimbledon, but I would proffer that Roddick does not have two grass court wins as good as Lendl's wins over Edberg and Becker.