When person asks a question, "which language is the most similar to Modern English?", the most common answer is:
Frisian
But most people that answer this question as it is, are unaware, which Frisian language/dialect. As far as I know, there are couple of Frisian languages/dialects, such as North Frisian, West Frisian, Saterland Frisian, Sölring, Öömrang, Fering, Halunder, Halligen, Wiringhiirder, Frasch, Karhiirder, Hoolmer and Hoorninger. Also, I think that is no such thing as Standard Frisian. (Or even Standard North Frisian, Standard Saterland Frisian or Standard West Frisian.)