The greatest thing about baseball is the teamwork.
Literal
Baseball [gen-の] most wonderful place [topic-は] teamwork [copula-だ].
ところ ('place') here functions metaphorically as 'point, aspect' — 最もすばらしいところ = 'the most wonderful aspect.' A productive extension of the core 'place' sense. 最も ('most') is the formal/written intensifier (vs. いちばん, more casual).