$epsilon gtrsim varepsilon$

documentclass{article}

begin{document}

  $varepsilon gtrsim epsilon$

end{document}

usepackage{mathptmx}

documentclass{article}
usepackage{newtxtext,newtxmath}
begin{document}
$epsilon=varepsilon$
end{document}

documentclass{article}
usepackage{mathptmx}
DeclareSymbolFont{epsilon}{OML}{ntxmi}{m}{it}
DeclareMathSymbol{epsilon}{mathord}{epsilon}{"0F}

begin{document}
$epsilon=varepsilon$
end{document}

documentclass{article}
usepackage{mathptmx}
DeclareSymbolFont{epsilon}{OML}{cmm}{m}{it}
DeclareMathSymbol{epsilon}{mathord}{epsilon}{"0F}

begin{document}
$epsilon=varepsilon$
end{document}