すみません。何とか事故解決しました。
もしこう書けばより良いとアドバイス頂けたら幸いです。
Sub fun()
Dim fso, file, files
Dim folderPath As String: folderPath = "G:\Test\"
Set fso = CreateObject("Scripting.FileSystemObject")
Set files = fso.GetFolder(folderPath).files

Dim j As Integer

For Each file In files
Dim wb As Workbook
'Set wb = Workbooks.Open(file)

Dim ts As Object
Set ts = fso.OpenTextFile(file)
Dim i As Integer: i = 1
j = j + 1
Do Until ts.AtEndOfStream
Cells(j, i).Value = ts.ReadLine
i = i + 1
Loop
ts.Close
'Call wb.Close(SaveChanges:=False)
Next file
End Sub