5) Viewtiful Joe: Double Trouble
It feels like every new installment in the Viewtiful Joe series became more and more obscure. Everybody still remembers the original, but the direct sequel is already lost somewhere deep in the annals of history. As for the rest of this unlucky series, I think Double Trouble for Nintendo DS definitely takes the biggest prize in the competition for least known installment. Granted, Double Trouble is not as well-designed as the previous entries, but it still has many creative ideas and should be at least remembered for being experimental in an already original series like Viewtiful Joe.