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New York has long maintained its solitary standing, if only in terms of sheer scale.
Literal
New-York [topic-は] only scale [gen-の] point [in-で] long-time solitary-eminence [obj-を] has-maintained.
ただ~の点で 'only in the respect of X' narrows the scope of a claim — here 'only in terms of scale.' 孤高 '(standing) solitary and high' is a literary compound for 'aloofness / solitary eminence,' applied to someone or something that stands alone above others. 保ってきた combines 保つ 'maintain' with ~てくる in its 'up-till-now temporal' sense — 'has been maintaining up to now' — a use distinct from the spatial or change-over-time senses of ~てくる.