My instinct evaluated Fowler only among CFB peers. In that regard, I really enjoy him and gave him an overall rating of a 4.
Over recent years, he has gotten more emotional as he's announced football games, punctuating several plays a quarter with elevated pitch and volume. To my ears, it works, because it sounds genuine and appreciative of the effort and skill on display by young men in their late teens and early 20s. This doesn't work well in the NFL unless your name is Kevin Harlan. He's better (by a significant margin) on the college game than Tessitore, who also raises his voice frequently, but with less command of the moment and much less purpose. I don't get much of a whiff of bias from Fowler, either, so it is possible to really just enjoy the game he's calling between two good programs.
I watch very little tennis, but as I reflect on Fowler in those circumstances, his tone is almost the opposite of his CFB persona. In tennis, he is quiet, calm, and reverential during play (in deference to the sport's etiquette), but also does well in setting the stage before matches and during breaks.
In both environment I feel like he sets up his color analyst partners well and complements their skills.
His passion for both sports comes through in his focus and dedication. In this regard, I think it sets him apart from other multi-sport PBP folks like Nantz, Tirico, et al.