My favorite characters to play as in Tatsunoko vs. Capcom are the following below.
From Tatsunoko:
Yatterman-1: Awesome hyper combos (especially the bulldozer attack where he rams Yatter-Wan through the battlefield), a quick fighter, great comboing, long range moves and awesome shiny teethes.
Tekkaman Blade: Awesome comboing, a useful (and cheap) special attack, hyper combos made of win (like his finisher), really powerful and has long range moves.
Jun The Swan: Looks cute, has a powerful yo-yo attack, one of the best finishers in the games, and makes a massively powerful combination with Ken The Eagle.
From Capcom:
Ryu: Simple controls